Compound and double angle formulaeEdexcel A-Level Maths: Flashcards

What these 13 flashcards ask

\sin(A+B)?
\cos(A+B)?
\tan(A-B)?
\sin2A?
Three forms of \cos2A?
\tan2A?
How do you get the double angle formulae?
Exact value of \sin75^\circ?
Which form of \cos2\theta for an equation also containing \sin\theta?
For \sin2x=k with 0\le x<360^\circ, what interval do you solve 2x in?
Why not divide by \sin\theta when solving?
a\cos\theta+b\sin\theta in the form R\cos(\theta-\alpha): R and \alpha?
Maximum of R\cos(\theta-\alpha) and where?

Exam questions on Compound and double angle formulae

Angles $A$ and $B$ are acute, with $\sin A=\frac{3}{5}$ and $\cos B=\frac{5}{13}$ .
Find the exact value of $\tan(A+B)$ .2 marks
The angle $x$ is acute and $\tan x=\frac{3}{4}$ .
Hence find the exact value of $\cos4x$ .2 marks
Consider the equation $\cos2\theta+3\sin\theta=2$ , where $0\le\theta<360^\circ$ .
Show that the equation can be written as $2\sin^2\theta-3\sin\theta+1=0$ .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).