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IB Math AA SL Revision Notes

Formulas, conditions, key connections and common exam traps across the five AA SL topics. Use it alongside the formula booklet and regular question practice.

Abdulhamid, IB Math tutor

Written by IB Math tutor Abdulhamid

IB Math Master ยท Updated

For the current AA SL syllabus, for exams up to November 2028.

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How to use these notes

Each topic is split into short sections. Every section keeps its formulas, conditions and diagrams together.

  • Connection (blue dot): links between formulas that the formula booklet does not state.
  • Exam note (gold diamond): short reminders and common traps.
  • Video: a link to my explanation of the topic.

Topic 1 Number and Algebra

Exponents and Logarithms

Exponent laws

NameFormulaCondition
Same base
amร—an=am+naman=amโˆ’n
a>0, m,nโˆˆโ„š
Powers of products
(am)n=amn(ab)n=anbn(ab)n=anbn
a,b>0
Zero and negative
a0=1aโˆ’n=1an
aโ‰ 0
Fractional
a1n=anamn=(an)m=amn
a>0
Standard form
aร—10k
1โ‰คa<10, kโˆˆโ„ค
  • Connection: a=a12 and 1a=aโˆ’12
  • Connection: Standard form products: multiply the a parts, add the powers of 10, then rescale to 1โ‰คa<10.

Logarithms

NameFormulaCondition
Definition of a log
ax=bโ€…โ€ŠโŸบโ€…โ€Šx=logโกab
a>0, b>0, aโ‰ 1
Inverses
logโกaax=x=alogโกax
x>0 on the right
Base e
ax=exlnโกa
a>0
Product and quotient
logโกa(xy)=logโกax+logโกaylogโกaxy=logโกaxโˆ’logโกay
x,y>0
Power
logโกa(xm)=mlogโกax
x>0
Change of base
logโกba=logโกcalogโกcb
a,b,c>0, b,cโ‰ 1
Base 10 and base e
logโกx=logโก10xlnโกx=logโกex
eโ‰ˆ2.718
  • Connection: logโกa1=0 and logโกaa=1
  • Connection: elnโกx=x and lnโก(ex)=x
  • Connection: logโกa1x=โˆ’logโกax
  • Connection: logโกba=1logโกab
  • Connection: logโกanx=1nlogโกax
  • Connection: ax=bย โ‡’ย x=logโกab=lnโกblnโกa
  • Exam note: No law exists for logโก(x+y), (logโกx)2 or (logโกx)(logโกy). Leave them as they are.
  • Exam note: logโกaf(x) exists only when f(x)>0. Reject any answer that makes f(x)โ‰ค0.

Back to topics

Sequences and Series

Arithmetic and geometric sequences

ItemArithmetic common difference dGeometric common ratio r
nth term
un=u1+(nโˆ’1)d
un=u1rnโˆ’1
Sum of n terms
Sn=n2(2u1+(nโˆ’1)d)=n2(u1+un)

Sn=u1(rnโˆ’1)rโˆ’1=u1(1โˆ’rn)1โˆ’r, rโ‰ 1

Sum to infinity

Sโˆž=u11โˆ’r, only when |r|<1

Finding d or r
u2โˆ’u1=u3โˆ’u2=โ‹ฏ=d
u2u1=u3u2=โ‹ฏ=r
  • Connection: For any sequence:
    S1=u1
    S2=u1+u2
    S3=u1+u2+u3
    un=Snโˆ’Snโˆ’1 for nโ‰ฅ2
  • Exam note: n counts terms, so nโˆˆโ„ค+.

Sigma notation

NameFormulaCondition
Sigma notation
โˆ‘i=1nui=u1+u2+โ‹ฏ+un
i runs through whole numbers
  • Connection: Sums split: โˆ‘(ai+bi)=โˆ‘ai+โˆ‘bi. Constants come out: โˆ‘cโ€‰ai=cโˆ‘ai.
  • Exam note: Check the first and last values of i.

Money: interest and depreciation

NameFormulaCondition
Compound interest
FV=PVร—(1+r100k)kn

FV = future value, PV = present value, n = number of years, k = number of compounding periods per year, r% = nominal annual rate of interest

geometric, ratio 1+r100k per period
Depreciation
Vn=V0ร—(1โˆ’r100)n

V0 = starting value, Vn = value after n years, r% = annual rate of depreciation

geometric, ratio 1โˆ’r100 per year

Back to topics

The Binomial Theorem

The binomial theorem

NameFormulaCondition
Factorial
n!=n(nโˆ’1)(nโˆ’2)โ‹ฏ2ร—1
0!=1
Combinations
nCr=n!r!โ€‰(nโˆ’r)!
Binomial theorem
(a+b)n=โˆ‘r=0nnCrโ€‰anโˆ’rbr=an+nC1โ€‰anโˆ’1b+โ‹ฏ+nCrโ€‰anโˆ’rbr+โ‹ฏ+bn
nโˆˆโ„•
General term
nCrโ€‰anโˆ’rbr
the term in br, r=0,1,โ€ฆ,n
Pascalโ€™s triangle
n=01
n=111
n=2121
n=31331
n=414641
n=515101051
row n gives nC0,ย nC1,ย โ€ฆ,ย nCn
  • Connection: n!=n(nโˆ’1)(nโˆ’2)! for nโ‰ฅ2
  • Connection: nC0=nCn=1, nC1=n and nCr=nCnโˆ’r
  • Connection: (a+b)n has n+1 terms. In each term, the powers of a and b add up to n.
  • Exam note: A coefficient is the number only. A term includes the power of x.
  • Exam note: In (aโˆ’b)n, use โˆ’b as the second term. The signs alternate.
  • Exam note: Bracket the whole term: (2x)r=2rxr, not 2xr.

Back to topics

Proof

Deductive proof

NameFormulaCondition
Identity

The symbol โ‰ก means true for every value. In an equation, = holds for some values only.

LHS to RHS

Start from one side. Change it one step at a time until it becomes the other side.

LHS =โ‹ฏ= RHS
  • Connection: Even numbers: 2m. Odd numbers: 2mยฑ1. Consecutive integers: n, n+1. Here m,nโˆˆโ„ค.
  • Exam note: LHS to RHS: work on one side only. Do not rewrite the whole identity on every line.

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Topic 2 Functions

Lines and Quadratics

Straight lines

NameFormulaCondition
Straight line
y=mx+cax+by+d=0yโˆ’y1=m(xโˆ’x1)
Gradient
m=y2โˆ’y1x2โˆ’x1
x1โ‰ x2
Parallel lines
m1=m2
Perpendicular lines
m1ร—m2=โˆ’1m2=โˆ’1m1
m1โ‰ 0

The three forms of a quadratic

FormEquationWhat it shows
Standard
f(x)=ax2+bx+c
y-intercept (0,c)
axis of symmetry x=โˆ’b2a
vertex (โˆ’b2a,ย f(โˆ’b2a))
Factor
f(x)=a(xโˆ’p)(xโˆ’q)
x-intercepts (p,0), (q,0)
axis of symmetry x=p+q2
Vertex
f(x)=a(xโˆ’h)2+k
vertex (h,k)
axis of symmetry x=h
  • Connection: a>0: minimum at the vertex. a<0: maximum at the vertex.
๐‘ฅ๐‘ฆaxisofsymmetry๐‘ฅ=30,๐‘=0,5๐‘=1๐‘ž=5โ„Ž,๐‘˜=3,โˆ’4
f(x)=x2โˆ’6x+5=(xโˆ’1)(xโˆ’5)=(xโˆ’3)2โˆ’4

Roots and the discriminant

NameFormulaCondition
Quadratic formula
ax2+bx+c=0ย โ‡’ย x=โˆ’bยฑb2โˆ’4ac2a
aโ‰ 0
Discriminant
ฮ”=b2โˆ’4ac
ฮ”>0

two distinct real roots: the graph crosses the x-axis twice

๐‘ฅ
ฮ”=0

two equal real roots: the graph touches the x-axis

๐‘ฅ
ฮ”<0

no real roots: the graph misses the x-axis

๐‘ฅ
Always positive

f(x)>0 for all xโ€…โ€ŠโŸบโ€…โ€Ša>0 and ฮ”<0

๐‘ฅ
Always negative

f(x)<0 for all xโ€…โ€ŠโŸบโ€…โ€Ša<0 and ฮ”<0

๐‘ฅ
  • Exam note: โ€œReal rootsโ€ means ฮ”โ‰ฅ0. โ€œTwo distinct real rootsโ€ means ฮ”>0.

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Functions, Composites and Inverses

Functions and composites

NameFormulaCondition
Function

Each x in the domain gives exactly one y

Domain, range

Domain: the allowed inputs. Range: the outputs.

Composite
(fโˆ˜g)(x)=f(g(x))
apply g first
  • Connection: In general fโˆ˜gโ‰ gโˆ˜f.

Inverse functions

NameFormulaCondition
Inverse

y=f(x): swap x and y, then make y the subject. f must be one-to-one.

Identity
(fโˆ˜fโˆ’1)(x)=(fโˆ’1โˆ˜f)(x)=x
  • Connection: The graph of fโˆ’1 is the reflection of f in y=x.
  • Connection: Domain of fโˆ’1 = range of f
    Range of fโˆ’1 = domain of f
  • Exam note: fโˆ’1(x) is not 1f(x).
๐‘ฅ๐‘ฆ๐‘ฆ=๐‘ฅ๐‘“๐‘“โˆ’1
(1,2) on f and (2,1) on fโˆ’1

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Graphs and Transformations

Transformations of y=f(x)

New graphTransformationPoint (x,y) moves to
y=f(x)+b
translation b units up
(x,ย y+b)
y=f(x)โˆ’b
translation b units down
(x,ย yโˆ’b)
y=f(xโˆ’a)
translation a units to the right
(x+a,ย y)
y=f(x+a)
translation a units to the left
(xโˆ’a,ย y)
y=โˆ’f(x)
reflection in the x-axis
(x,ย โˆ’y)
y=f(โˆ’x)
reflection in the y-axis
(โˆ’x,ย y)
y=pf(x)
vertical stretch, scale factor p
(x,ย py)
y=f(qx)
horizontal stretch, scale factor 1q
(xq,ย y)
  • Exam note: In this table a,b,p,q>0. So f(x)+b always moves up and f(x)โˆ’b always moves down.
  • Connection: Inside the bracket: changes x and works the opposite way to how it looks.
  • Connection: Outside the bracket: changes y and works the way it looks.
  • Connection: y=pf(x)+b: stretch first, then translate.
  • Exam note: Describe each transformation fully: type, direction and scale factor or distance.
๐‘ฅ๐‘ฆ+2๐‘ฅ๐‘ฆรท2
Dashed y=x2. Left: y=(xโˆ’2)2 moves right 2. Right: y=(2x)2 divides each x by 2.

Sketching

  • Exam note: Label key features on a sketch: intercepts, turning points, asymptotes and domain end points.
  • Exam note: Paper 2: find intersections, zeros and turning points with the GDC.

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Rational Functions

Types and their asymptotes

Typef(x)AsymptotesExample
Reciprocal
1x

vertical x=0

horizontal y=0

self-inverse: fโˆ’1(x)=1x

Linear over linear
ax+bcx+d

vertical: where the denominator cx+d=0

horizontal y=ac

๐‘ฅ๐‘ฆ
y=2x+1xโˆ’1

Finding asymptotes and intercepts

  • Connection: Vertical asymptote: the x that makes the denominator 0 (numerator โ‰ 0).
  • Connection: x-intercept: put y=0. y-intercept: put x=0.
  • Connection: Horizontal asymptote, compare degrees:
    top < bottom: y=0
    top = bottom: y= ratio of leading coefficients
  • Exam note: Write asymptotes as equations.

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Exponential and Logarithmic Functions

The two graphs

NameFormulaCondition
Exponential
f(x)=axf(x)=exa>0,ย aโ‰ 1
domain โ„, range y>0
asymptote y=0, through (0,1)
Logarithmic
f(x)=logโกaxf(x)=lnโกx
domain x>0, range โ„
asymptote x=0, through (1,0)
  • Connection: ax and logโกax are inverses: reflections in y=x. The same holds for ex and lnโกx.
๐‘ฅ๐‘ฆ๐‘ฆ=๐‘ฅ๐‘ฆ=๐‘’๐‘ฅ๐‘ฆ=ln๐‘ฅ11

Changing the graphs

  • Connection: a>1: increasing. 0<a<1: decreasing.
  • Connection: aโˆ’x=(1a)x: the reflection of ax in the y-axis
  • Connection: y=Aekx+c: asymptote y=c. k>0: growth. k<0: decay.
  • Connection: logโกag(x) needs g(x)>0. Its vertical asymptote is where g(x)=0.
  • Exam note: Translations move the asymptote too.
  • Exam note: In y=Aekt+c, the value at t=0 is A+c, not A.

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Solving Equations and Inequalities

Using graphs

NameFormulaCondition
Graphical solution

Solutions of f(x)=g(x) are the x-coordinates where the graphs meet

  • Connection: Number of solutions = number of intersection points

Quadratic inequalities

NameFormulaCondition
Roots ฮฑ<ฮฒ, a>0

ax2+bx+c>0โ€…โ€ŠโŸบโ€…โ€Šx<ฮฑ or x>ฮฒ

ax2+bx+c<0โ€…โ€ŠโŸบโ€…โ€Šฮฑ<x<ฮฒ

  • Exam note: Sketch the graph, then read off where it is above or below the x-axis.
  • Exam note: Multiplying or dividing by a negative number reverses the inequality.
๐‘ฅ๐›ผ๐›ฝ++โˆ’

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Topic 3 Geometry and Trigonometry

3D Geometry and Triangles

Points in 3D

NameFormulaCondition
Distance
d=(x1โˆ’x2)2+(y1โˆ’y2)2+(z1โˆ’z2)2
Midpoint
(x1+x22,ย y1+y22,ย z1+z22)

Solids

NameFormulaCondition
Right pyramid
V=13Ah, A = area of base, h = height
Right cone
V=13ฯ€r2h curved surface A=ฯ€rl
total surface =ฯ€rl+ฯ€r2 l2=r2+h2, l = slant height
Sphere
V=43ฯ€r3A=4ฯ€r2
Hemisphere
V=23ฯ€r3 curved surface 2ฯ€r2
โ„Ž๐‘Ÿ๐‘™

Right-angled triangles

NameFormulaCondition
Ratios
sinโกฮธ=opphypcosโกฮธ=adjhyptanโกฮธ=oppadj
Pythagoras
a2+b2=c2, c = hypotenuse
๐œƒadjacentoppositehypotenuse
Opposite and adjacent are named from ฮธ.

Angles of elevation and depression

  • Exam note: Angles of elevation and depression are measured from the horizontal.
  • Connection: The angle of elevation of B from A equals the angle of depression of A from B.
horizontal๐ด๐ตelevationdepression
Both angles are measured from the horizontal.

Any triangle

NameFormulaCondition
Sine rule
asinโกA=bsinโกB=csinโกC
Cosine rule
c2=a2+b2โˆ’2abcosโกC
cosโกC=a2+b2โˆ’c22ab
Area
A=12absinโกC
๐ด๐ต๐ถ๐‘๐‘Ž๐‘
Side a is opposite angle A, and so on.
Use the sine rule when you knowUse the cosine rule when you know
  • two angles and one side
  • two sides and an angle not between them
    (this can be the ambiguous case)
  • two sides and the angle between them
  • all three sides
  • Exam note: Set the GDC to degrees or radians to match the question.

The ambiguous case of the sine rule

  • Exam note: It happens only when you know two sides and an angle not between them, and you use the sine rule to find an angle.
  • Exam note: sinโกฮธ=k gives two angles: ฮธ and 180โˆ˜โˆ’ฮธ. Check both. Keep 180โˆ˜โˆ’ฮธ only if the angles of the triangle still add up to 180โˆ˜ with every angle positive.
๐‘๐‘Ž๐‘Ž๐ด๐ถ1๐ถ2๐ต
Ambiguous case only: two triangles fit the same A, c and a.

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Radians and the Unit Circle

Radians, arcs and sectors

NameFormulaCondition
Radians
ฯ€ย radians=180โˆ˜
Arc length
l=rฮธ
ฮธ in radians
Sector area
A=12r2ฮธ
ฮธ in radians
๐‘Ÿ๐‘™=๐‘Ÿ๐œƒ๐œƒ๐ด
  • Exam note: Arc length and sector area need ฮธ in radians.

The unit circle and exact values

NameFormulaCondition
Unit circle
cosโกฮธ=x-coordinate
sinโกฮธ=y-coordinate
Tan
tanโกฮธ=sinโกฮธcosโกฮธ,ย cosโกฮธโ‰ 0
ฮธ0ฯ€6ฯ€4ฯ€3ฯ€2
sinโกฮธ
0
12
22
32
1
cosโกฮธ
1
32
22
12
0
tanโกฮธ
0
33
1
3

undefined

  • Exam note: Exact values of multiples: find the reference angle, then the sign from the quadrant.

The full unit circle is on the next page.

The unit circle

๐‘ฅ๐‘ฆ๐‘‚00โˆ˜1,0๐œ‹630โˆ˜32,12๐œ‹445โˆ˜22,22๐œ‹360โˆ˜12,32๐œ‹290โˆ˜0,12๐œ‹3120โˆ˜โˆ’12,323๐œ‹4135โˆ˜โˆ’22,225๐œ‹6150โˆ˜โˆ’32,12๐œ‹180โˆ˜โˆ’1,07๐œ‹6210โˆ˜โˆ’32,โˆ’125๐œ‹4225โˆ˜โˆ’22,โˆ’224๐œ‹3240โˆ˜โˆ’12,โˆ’323๐œ‹2270โˆ˜0,โˆ’15๐œ‹3300โˆ˜12,โˆ’327๐œ‹4315โˆ˜22,โˆ’2211๐œ‹6330โˆ˜32,โˆ’12allpositivesinpositivetanpositivecospositive
Each point is (cosโกฮธ,ย sinโกฮธ). Angles are measured anticlockwise from the positive x-axis. tanโกฮธ=yx.

Example: ฮธ=30โˆ˜=ฯ€6

The point on the unit circle at 30โˆ˜ is (32,ย 12).

cosโก30โˆ˜=x-coordinate =32

sinโก30โˆ˜=y-coordinate =12

tanโก30โˆ˜=yx=1232=13=33

๐‘ฅ๐‘ฆ1cos30โˆ˜=32sin30โˆ˜=1230โˆ˜32,12

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Trigonometric Identities

Pythagorean and double angle identities

NameFormulaCondition
Pythagorean
cosโก2ฮธ+sinโก2ฮธ=1
Double angle
sinโก2ฮธ=2sinโกฮธcosโกฮธ
cosโก2ฮธ=cosโก2ฮธโˆ’sinโก2ฮธ=2cosโก2ฮธโˆ’1=1โˆ’2sinโก2ฮธ
  • Connection: cosโก2ฮธ=1+cosโก2ฮธ2 and sinโก2ฮธ=1โˆ’cosโก2ฮธ2
  • Exam note: sinโก2ฮธโ‰ 2sinโกฮธ.
  • Exam note: Pick the cosโก2ฮธ form that matches the rest of the equation: all sin or all cos.

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Trigonometric Functions

The three graphs

NameFormulaCondition
sinโกx, cosโกx
period 2ฯ€ range โˆ’1โ‰คyโ‰ค1
sin (blue). cos (dark).
๐‘ฅ๐‘ฆ1โˆ’1๐œ‹2๐œ‹
tanโกx
period ฯ€
asymptotes x=ฯ€2+kฯ€, kโˆˆโ„ค
๐‘ฅ

Transformed sine and cosine

NameFormulaCondition
Functions
f(x)=asinโก(b(xโˆ’c))+df(x)=acosโก(b(xโˆ’c))+d
b>0
FeatureFrom the functionFrom the graph
Amplitude
|a|
maxโˆ’min2
Period
radians: 2ฯ€b
degrees: 360โˆ˜b

from a maximum to the next maximum, or from a minimum to the next minimum

then b=2ฯ€period or b=360โˆ˜period

Principal axis
y=d
y=max+min2
Maximum, minimum
d+|a|,ย dโˆ’|a|

the highest and lowest y-values

Horizontal shift

c to the right
(c<0: to the left)

sine with a>0: the x where the graph crosses y=d going up
cosine with a>0: the x of a maximum point

  • Connection: Example: amplitude 1.5, period 2ฯ€2=ฯ€, principal axis y=2, shift ฯ€4 to the right, maximum 2+1.5=3.5, minimum 2โˆ’1.5=0.5.
๐‘ฅ๐‘ฆ๐‘ฆ=2๐œ‹4๐œ‹2๐œ‹3๐œ‹2๐‘=๐œ‹41.5min=2โˆ’1.5=0.5period=๐œ‹max=3.5
f(x)=1.5sinโก(2(xโˆ’ฯ€4))+2: a=1.5, b=2, c=ฯ€4, d=2

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Topic 4 Statistics and Probability

Data and Statistics

Mean and spread

NameFormulaCondition
Mean
xยฏ=โˆ‘fixin
n=โˆ‘fi
Variance
ฯƒ2=โˆ‘fi(xiโˆ’ฮผ)2n=โˆ‘fixi2nโˆ’ฮผ2
Standard deviation
ฯƒ=โˆ‘fi(xiโˆ’ฮผ)2n
Grouped data

use mid-interval values as xi

gives an estimate
Change to every valueMeanStandard deviation ฯƒVariance ฯƒ2IQR
Add k to every value
mean+k
unchanged
unchanged
unchanged
Subtract k from every value
meanโˆ’k
unchanged
unchanged
unchanged
Multiply every value by k
meanร—k
ฯƒร—|k|
ฯƒ2ร—k2
IQRร—|k|
Divide every value by k, kโ‰ 0
meanรทk
ฯƒรท|k|
ฯƒ2รทk2
IQRรท|k|
  • Connection: Adding or subtracting k moves every value by the same amount, so the spread does not change.
  • Connection: Example: 2, 4, 6 has mean 4. Add 10 to every value: 12, 14, 16, mean 14, same spread. Multiply every value by 3: 6, 12, 18, mean 12, and ฯƒ is 3 times larger.
  • Exam note: Use ฯƒx from the GDC, not sx.

Quartiles, outliers and box plots

NameFormulaCondition
Interquartile range
IQR=Q3โˆ’Q1
Outlier

below Q1โˆ’1.5ร—IQR or above Q3+1.5ร—IQR

Cumulative frequency

read across at n4 for Q1, n2 for the median, 3n4 for Q3

percentile p: at p% of n
0123456789101112131415161718min=1๐‘„1=4median=8๐‘„3=13max=16IQR=13โˆ’4=9
Data: 1, 3, 4, 6, 7, 8, 10, 11, 13, 14, 16. Read each value from the scale.

Sampling and data

NameFormulaCondition
Population, sample

The population is the whole group being studied. A sample is part of it.

Simple random sample

Every possible sample of that size is equally likely to be chosen.

Bias, reliability

A biased sample does not represent the population. Check that the source of the data is reliable.

Frequency distribution

A table of values or classes with their frequencies. A histogram shows it as bars with no gaps.

Mode, modal class

The value with the highest frequency. For grouped data: the class with the highest frequency.

  • Connection: Sampling methods: simple random, systematic, stratified, quota, convenience
  • Exam note: Discrete data is counted. Continuous data is measured.

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Correlation and Regression

Correlation

NameFormulaCondition
Pearsonโ€™s r
โˆ’1โ‰คrโ‰ค1
from the GDC
  • Connection: r close to ยฑ1: strong linear correlation. r close to 0: weak or no linear correlation. The sign of r gives the direction.
  • Connection: Scatter diagram: plot each pair (x,y) as a point. A line of best fit drawn by eye passes through the mean point (xยฏ,yยฏ).
  • Exam note: Correlation does not mean causation.

Regression lines

NameFormulaCondition
y on x

y=ax+b: predicts y from x

x on y

x=cy+d: predicts x from y

  • Connection: For each increase of 1 in x, y changes by a.
    When x=0, y=b.
  • Connection: Both lines pass through (xยฏ,yยฏ).
  • Exam note: The y on x line predicts y from x only. Using it to predict x from y is not reliable: use the x on y line.
  • Exam note: Interpolation is reliable when the correlation is strong (r is close to ยฑ1). Extrapolation is not reliable.
๐‘ฅ๐‘ฆ๐‘ฆon๐‘ฅ๐‘ฅon๐‘ฆ๐‘ฅฬ„๐‘ฆฬ„
Both lines pass through (xยฏ,yยฏ)

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Probability

Basic rules

NameFormulaCondition
Probability of A

P(A)=n(A)n(U), equally likely outcomes

Complementary events
P(A)+P(Aโ€ฒ)=1
Combined events
P(AโˆชB)=P(A)+P(B)โˆ’P(AโˆฉB)
Mutually exclusive
P(AโˆฉB)=0
so P(AโˆชB)=P(A)+P(B)
Expected number
np for n trials with probability p
๐ด๐ต๐‘ˆ๐ดโˆฉ๐ต:inboth๐ดand๐ต๐ด๐ต๐‘ˆ๐ดโˆช๐ต:in๐ดor๐ตorboth
P(A)+P(B) counts AโˆฉB twice, so subtract P(AโˆฉB) once.

Conditional probability and independence

NameFormulaCondition
Conditional
P(AโˆฃB)=P(AโˆฉB)P(B)
Independent
P(AโˆฉB)=P(A)โ€‰P(B)
  • Connection: Independent โ€…โ€ŠโŸบโ€…โ€ŠP(AโˆฃB)=P(A)=P(AโˆฃBโ€ฒ)
  • Connection: P(AโˆฉB)=P(AโˆฃB)โ€‰P(B)=P(BโˆฃA)โ€‰P(A)
  • Exam note: โ€œGiven thatโ€ means conditional: divide by the probability of the given event.

Tree diagrams

  • Connection: Tree diagram: multiply along branches and add the end results.
  • Exam note: Without replacement, the second-stage probabilities change.
0.010.990.950.050.080.92๐ต๐ต๐ด0.01ร—0.95๐ด๐ด0.99ร—0.08๐ด
P(BโˆฃA)=0.01ร—0.950.01ร—0.95+0.99ร—0.08

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Discrete Distributions

Discrete random variables

NameFormulaCondition
Probability distribution
โˆ‘P(X=x)=1
0โ‰คP(X=x)โ‰ค1
Expected value
E(X)=ฮผ=โˆ‘xโ€‰P(X=x)
  • Connection: Fair game: E(gain)=0

Binomial distribution

NameFormulaCondition
Binomial
XโˆผB(n,p)ย โ‡’ย P(X=x)=nCxโ€‰px(1โˆ’p)nโˆ’x
x=0,1,โ€ฆ,n
Mean and variance
E(X)=npVarโก(X)=np(1โˆ’p)
  • Connection: Conditions: fixed n, two outcomes (success and failure), constant p, independent trials
  • Connection: P(Xโ‰ฅk)=1โˆ’P(Xโ‰คkโˆ’1)
    P(X>k)=1โˆ’P(Xโ‰คk)
  • Exam note: GDC: binomial pdf for P(X=x) and binomial cdf for P(Xโ‰คx).
  • Exam note: โ€œAt leastโ€, โ€œmore thanโ€ and โ€œfewer thanโ€: rewrite with โ‰ค before using the cdf.
0123456P๐‘‹โ‰ค2P๐‘‹โ‰ฅ3
XโˆผB(6,0.4): P(Xโ‰ฅ3)=1โˆ’P(Xโ‰ค2)

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The Normal Distribution

The normal curve

NameFormulaCondition
Normal
XโˆผN(ฮผ,ฯƒ2)
ฯƒ2= variance
Properties

symmetric about ฮผ, mean = median = mode, total area 1

  • Connection: Normal probabilities such as P(a<X<b): use the normal cdf on the GDC with the lower bound, the upper bound, ฮผ and ฯƒ.
  • Exam note: N(ฮผ,ฯƒ2) gives the variance. Take the square root for ฯƒ.

The empirical rule

๐œ‡โˆ’3๐œŽ20๐œ‡โˆ’2๐œŽ30๐œ‡โˆ’๐œŽ40๐œ‡50๐œ‡+๐œŽ60๐œ‡+2๐œŽ70๐œ‡+3๐œŽ8034.13%34.13%13.59%13.59%2.14%2.14%0.13%0.13%about68%about95%about99.7%
Blue numbers: the example XโˆผN(50,102), so ฮผ=50 and ฯƒ=10. Each percentage is the area to 2 decimal places.

Using symmetry: an example

  • Connection: XโˆผN(50,102)
  • Connection: P(X<50)=0.5
  • Connection: P(X<40)=P(X>60), because 40 and 60 are both 10 from the mean.
  • Connection: P(X=45)=0, so P(X<45)=P(Xโ‰ค45).
405060P๐‘‹<40P๐‘‹>60
XโˆผN(50,102): the two gold areas are equal.

Standardising and the inverse normal

NameFormulaCondition
Standardised variable
z=xโˆ’ฮผฯƒ
ZโˆผN(0,1)
  • Connection: ฮผ or ฯƒ unknown, with a given probability such as P(X<x)=p:
    1. Standardise with the z formula: P(X<x)=P(Z<xโˆ’ฮผฯƒ)=p, where ZโˆผN(0,1).
    2. Use the inverse normal on N(0,1), with mean 0 and standard deviation 1, to find the z-value with P(Z<z)=p.
    3. Set xโˆ’ฮผฯƒ=z and solve for the unknown.
  • Connection: Example: XโˆผN(ฮผ,42) and P(X<30)=0.9. Inverse normal: z=1.2816. So 30โˆ’ฮผ4=1.2816, giving ฮผ=24.87 (2 d.p.).
  • Connection: Both ฮผ and ฯƒ unknown: two probabilities are given. Do steps 1 to 3 for each one. This gives two equations in ฮผ and ฯƒ. Solve them together.
  • Exam note: Inverse normal: check which tail the GDC uses.

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Topic 5 Calculus

Limits and the Derivative

Limits

NameFormulaCondition
Limit
limโกxโ†’af(x): the value f(x) approaches as xโ†’a

The derivative

NameFormulaCondition
Derivative
y=f(x)ย โ‡’ย dydx=fโ€ฒ(x)

the gradient function and the rate of change of y with respect to x

Second derivative
fโ€ณ(x)=d2ydx2
๐‘ฅ๐‘ฆ๐‘ฅ๐‘ฅ+โ„Žchordtangent
As hโ†’0 the chord turns into the tangent.

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Differentiation Rules

Standard derivatives

f(x)fโ€ฒ(x)
xn
nxnโˆ’1
sinโกx
cosโกx
cosโกx
โˆ’sinโกx
f(x)fโ€ฒ(x)
ex
ex
lnโกx
1x
  • Exam note: Trig derivatives need x in radians.

Chain, product and quotient rules

NameFormulaCondition
Chain rule
y=g(u), where u=f(x)ย โ‡’ย dydx=dyduร—dudx
Product rule
y=uvย โ‡’ย dydx=udvdx+vdudx
Quotient rule
y=uvย โ‡’ย dydx=vdudxโˆ’udvdxv2
  • Connection: ddxf(ax+b)=aโ€‰fโ€ฒ(ax+b)
  • Connection: ddxeg(x)=gโ€ฒ(x)โ€‰eg(x) and ddxlnโกg(x)=gโ€ฒ(x)g(x)
  • Connection: ddx[g(x)]n=n[g(x)]nโˆ’1gโ€ฒ(x)
  • Exam note: Simplify first: split fractions and use log laws before differentiating.

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Using Derivatives

Shape of a graph

IfThen

fโ€ฒ(x)>0

f is increasing

fโ€ฒ(x)<0

f is decreasing

fโ€ฒ(a)=0

stationary point at x=a

fโ€ฒ(a)=0 and fโ€ณ(a)<0

local maximum at x=a

fโ€ฒ(a)=0 and fโ€ณ(a)>0

local minimum at x=a

fโ€ฒ(a)=0 and fโ€ณ(a)=0

the test fails: check the sign of fโ€ฒ on each side of a

fโ€ฒ(a)=0, fโ€ณ(a)=0 and fโ€ณ changes sign at a

horizontal (stationary) point of inflection at x=a

fโ€ณ(x)>0

concave up

fโ€ณ(x)<0

concave down

fโ€ณ(a)=0 and fโ€ณ changes sign at a

point of inflection at x=a

  • Connection: Second derivative test: first solve fโ€ฒ(x)=0 to find the stationary point x=a. Then test the sign of fโ€ณ(a).
  • Connection: f turns where fโ€ฒ=0 and fโ€ฒ changes sign. f has an inflection where fโ€ฒ turns.
  • Connection: Horizontal (stationary) inflection: the tangent is horizontal, fโ€ฒ=0 there. Non-stationary inflection: fโ€ฒโ‰ 0 there.
  • Exam note: fโ€ณ(a)=0 alone does not prove an inflection. Check the sign change.
๐‘ฅ๐‘“๐‘ฅ๐‘Ž=โˆ’1:๐‘“๐‘Ž=0๐‘“๐‘Ž=โˆ’6<0:max๐‘Ž=1:๐‘“๐‘Ž=0๐‘“๐‘Ž=6>0:mininflection๐‘ฅ๐‘“๐‘ฅ
f(x)=x3โˆ’3x. Step 1: fโ€ฒ(x)=3x2โˆ’3=0 gives the turning points a=โˆ’1 and a=1.
Step 2: test each one with fโ€ณ(x)=6x. f has an inflection where fโ€ฒ turns.
๐‘ฅ๐‘ฆinflection1,2๐‘“1=0concavedown๐‘“๐‘ฅ<0concaveup๐‘“๐‘ฅ>0maxmin
f(x)=x3โˆ’3x2+4, fโ€ณ(x)=6xโˆ’6: concave down for x<1, concave up for x>1, inflection at (1,2).
๐‘ฅ๐‘ฆ๐‘“0=0,๐‘“0=0๐‘“changessign
f(x)=x3: a horizontal point of inflection at the origin. The tangent there is horizontal.

Sketching the first and second derivatives

Graph of fGraph of fโ€ฒGraph of fโ€ณ

increasing

above the x-axis
(fโ€ฒ>0)

decreasing

below the x-axis
(fโ€ฒ<0)

max or min

crosses the x-axis
(fโ€ฒ=0)

point of inflection

max or min

crosses the x-axis
(fโ€ณ=0)

concave up

increasing

above the x-axis
(fโ€ณ>0)

concave down

decreasing

below the x-axis
(fโ€ณ<0)

  • Connection: fโ€ฒ touches the x-axis without crossing: a horizontal point of inflection of f.
  • Exam note: Mark the x-values of the key points of f first. Then sketch fโ€ฒ through them.
012๐‘ฅ๐‘“maxmininflection๐‘ฅ๐‘“minof๐‘“๐‘ฅ๐‘“
f(x)=x3โˆ’3x2+2
Max at x=0 and min at x=2: fโ€ฒ crosses the axis.
Inflection at x=1: fโ€ฒ has its min and fโ€ณ crosses the axis.

Tangents and normals

  • Connection: Tangent at x=a: find the point (a,f(a)) and the gradient m=fโ€ฒ(a). Put them into the equation of a straight line.
  • Connection: Normal at x=a: the same point, with gradient โˆ’1m, because the normal is perpendicular to the tangent. If m=0, the normal is x=a.

Optimisation

  • Connection: Write the quantity in one variable, set the derivative to 0, then confirm max or min.
  • Exam note: Check the end points of the domain too.

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Integration

Standard integrals

โˆซxnโ€‰dx=xn+1n+1+C,nโ‰ โˆ’1
โˆซ1xโ€‰dx=lnโก|x|+C
โˆซsinโกxโ€‰dx=โˆ’cosโกx+C
โˆซcosโกxโ€‰dx=sinโกx+C
โˆซexโ€‰dx=ex+C
  • Exam note: Add +C to every indefinite integral. Keep the modulus in lnโก|x|.
  • Connection: A boundary condition finds C.

Recognising the form

NameFormulaCondition
Linear inside
โˆซf(ax+b)โ€‰dx=1aF(ax+b)+C
Fโ€ฒ=f
Top is the derivative of the bottom
โˆซgโ€ฒ(x)g(x)โ€‰dx=lnโก|g(x)|+C
Derivative times exponential
โˆซgโ€ฒ(x)โ€‰eg(x)โ€‰dx=eg(x)+C
  • Connection: sinโก2x, cosโก2x: use the double angle formula (Topic 3).

Substitution and definite integrals

NameFormulaCondition
Substitution
โˆซf(g(x))โ€‰gโ€ฒ(x)โ€‰dx: let u=g(x), du=gโ€ฒ(x)โ€‰dx, then find โˆซf(u)โ€‰du
Definite integral
โˆซabf(x)โ€‰dx=F(b)โˆ’F(a)
Fโ€ฒ=f
  • Connection: Example: โˆซ2x(x2+1)3โ€‰dx. Let u=x2+1, so du=2xโ€‰dx. This gives โˆซu3โ€‰du=u44+C=(x2+1)44+C.
  • Exam note: Substitution in a definite integral: change the limits to u-values too.

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Areas and Kinematics

Areas

NameFormulaCondition
With the x-axis
A=โˆซab|y|โ€‰dx
A=โˆซabyโ€‰dx when y>0
Between curves
A=โˆซab(f(x)โˆ’g(x))โ€‰dx,f(x)โ‰ฅg(x)
  • Connection: Below the x-axis, the integral is negative. Split at the roots or integrate |y|.
  • Exam note: Area between curves: find where they meet for the limits.
๐‘ฅ๐‘ฆ244โˆ’4
y=x(xโˆ’2)(xโˆ’4), 0โ‰คxโ‰ค4
area =4+4=8
integral =4+(โˆ’4)=0

Kinematics

NameFormulaCondition
Velocity, acceleration
v=dsdta=dvdt=d2sdt2
Going back
s=โˆซvโ€‰dtv=โˆซaโ€‰dt

use the starting values to find C

Displacement from t1 to t2
โˆซt1t2v(t)โ€‰dt
Distance travelled from t1 to t2
โˆซt1t2|v(t)|โ€‰dt
Speed
|v|
๐‘ก๐‘ฃ4โˆ’441349
v=3(tโˆ’1)(tโˆ’3), 0โ‰คtโ‰ค4
displacement =4+(โˆ’4)+4=4
distance =4+4+4=12
  • Connection: v>0: moving in the positive direction. v<0: moving in the negative direction.
  • Connection: At rest: v=0. Changes direction: v changes sign.
  • Connection: Speeding up: v and a have the same sign. Slowing down: opposite signs.
  • Connection: Maximum speed from a v–t graph: speed is |v|, so look for the point furthest from the t-axis. It can be above or below the axis.
๐‘ 0positivedirectionโŸถ๐‘ฃ>0:movingright๐‘ฃ=0and๐‘ฃchangessign:changesdirection๐‘ฃ<0:movingleft
Motion along a straight line: s is the displacement from 0.
๐‘ก๐‘ฃ14779๐‘ฃ=โˆ’9
v=(tโˆ’1)(tโˆ’7), 0โ‰คtโ‰ค7
Furthest from the t-axis: v=โˆ’9 at t=4, not v=7 at t=0.
Maximum speed =9.

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