Addition and double angle formulaeEdexcel International A Level Maths: Flashcards

What these 13 flashcards ask

\sin(A+B)=?
\sin(A-B)=?
\cos(A+B)=?
\cos(A-B)=?
\tan(A+B)=?
\tan(A-B)=?
\sin2A=?
Three forms of \cos2A?
\tan2A=?
How do you obtain double angle formulae from addition formulae?
Write \cos\theta in terms of \frac{\theta}{2} (two forms).
Exact value of \sin75^{\circ}?
\cos x\cos2x+\sin x\sin2x simplifies to what?

Exam questions on Addition and double angle formulae

The angle $A$ is acute and $\sin A=\frac{3}{5}$ .
Find the exact value of $\tan2A$ .2 marks
The angle $75^{\circ}$ can be written as $45^{\circ}+30^{\circ}$ , and exact values of the sine and cosine of $30^{\circ}$ and $45^{\circ}$ are known.
Hence find $\tan75^{\circ}$ in the form $a+\sqrt b$ , where $a$ and $b$ are integers.2 marks
Angles are measured in degrees.
Prove that $\cos x\cos2x+\sin x\sin2x\equiv\cos x$ .3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).