A-Level Maths Edexcel 9MA0

1.5: Trigonometry

#1.5.1

Sine, cosine and tangent

Understand and use the definitions of sine, cosine and tangent for all arguments.

Use of xx and yy coordinates of points on the unit circle to give cosine and sine respectively.

The sine and cosine rules, including the ambiguous case of the sine rule.

The area of a triangle in the form 12absinC\frac{1}{2}ab\sin{C}.

Work with radian measure, including use for arc length and area of sector.

Use of the formulae s=rθs = rθ and A=12r2θA = \frac{1}{2}r^2θ for arc lengths and areas of sectors of a circle.

#1.5.2

Small angle approximations

Understand and use the standard small angle approximations of sine, cosine and tangent

  • sinθθ\sin{θ}≈θ,
  • cosθ1θ22\cos{θ}≈1-\dfrac{θ^2}{2},
  • tanθθ\tan{θ}≈θ

Where θ is in radians.

Students should be able to approximate,

e.g. cos3x1xsin4x\dfrac{\cos{3x}-1}{x\sin{4x}} when xx is small, to 98-\dfrac{9}{8}.

#1.5.3

Trigonometric functions

Understand and use the sine, cosine and tangent functions; their graphs, symmetries and periodicity.

Knowledge of graphs of curves with equations such as y=sinxy = \sin{x}, y=cos(x+30°)y =\cos{(x + 30°)}, y=tan2xy =\tan{2x} is expected.

Know and use exact values of sin\sin and cos\cos for 0, π6\dfrac{\pi}{6}, π4\dfrac{\pi}{4}, π3\dfrac{\pi}{3}, π2\dfrac{\pi}{2}, π\pi and multiples thereof, and exact values of tan\tan for 0, π6\dfrac{\pi}{6}, π4\dfrac{\pi}{4}, π3\dfrac{\pi}{3}, π\pi and multiples thereof

#1.5.4

Reciprocal and inverse trigonometric functions

Understand and use the definitions of secant, cosecant and cotangent and of arcsin, arccos and arctan; their relationships to sine, cosine and tangent; understanding of their graphs; their ranges and domains.

Angles measured in both degrees and radians.

#1.5.5

Pythagorean identities

Understand and use

  • tanθ=sinθcosθ\tan{θ} = \dfrac{\sin{θ}}{\cos{θ}}
  • sin2θ+cos2θ=1\sin^2{θ} + \cos^2{θ} = 1
  • sec2θ=1+tan2θ\sec^2{θ} = 1 + \tan^2{θ} and
  • cosec2θ=1+cot2θ\cosec^2{θ} = 1 + \cot^2{θ}

These identities may be used to solve trigonometric equations and angles may be in degrees or radians. They may also be used to prove further identities.

#1.5.6

Compound angle and double angle formulae

Understand and use double angle formulae; use of formulae for sin(A±B)\sin{(A ± B)}, cos(A±B)\cos{(A ± B)}, and tan(A±B)\tan{(A ± B)}, understand geometrical proofs of these formulae.

To include application to half angles. Knowledge of the tan(12θ)\tan{(\frac{1}{2}θ)} formulae will not be required.

Understand and use expressions for acosθ+bsinθa\cos{θ} + b\sin{θ} in the equivalent forms of rcos(θ±α)r\cos{(θ±α)} or rsin(θ±α)r\sin{(θ±α)}

Students should be able to solve equations such as acosθ+bsinθ=ca\cos{θ} + b\sin{θ} = c in a given interval.

#1.5.7

Solve trigonometric equations

Solve simple trigonometric equations in a given interval, including quadratic equations in sin\sin, cos\cos and tan\tan and equations involving multiples of the unknown angle.

Students should be able to solve equations such as

  • sin(x+70°)=0.5\sin{(x + 70°)} = 0.5 for 0<x<360°0 < x < 360°,
  • 3+5cos2x=13 + 5\cos{2x} = 1 for 180°<x<180°-180° < x < 180°, and
  • 6cos2x+sinx5=06\cos^2{x} + \sin{x} − 5 = 0 for 0x<360°0 ≤ x < 360°

These may be in degrees or radians and this will be specified in the question.

#1.5.8

Trigonometric proof

Construct proofs involving trigonometric functions and identities.

Students need to prove identities such as cosxcos2x+sinxsin2xcosx\cos{x}\cos{2x} + \sin{x}\sin{2x} ≡ \cos{x}.

#1.5.9

Trigonometric modelling

Use trigonometric functions to solve problems in context, including problems involving vectors, kinematics and forces.

Problems could involve (for example) wave motion, the height of a point on a vertical circular wheel, or the hours of sunlight throughout the year. Angles may be measured in degrees or in radians.

1.4
Sequences and series
1.6
Exponentials and logarithms