Addition and double angle formulaeEdexcel International A Level Maths: Mind map

Exam questions on Addition and double angle formulae

1. The angle $A$ is acute and $\sin A=\frac{3}{5}$.
   Find the exact value of $\tan2A$.2 marks
2. 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
3. Angles are measured in degrees.
   Prove that $\cos x\cos2x+\sin x\sin2x\equiv\cos x$.3 marks