3.4 Trigonometry (A-level only)

a.

By writing $\cos 3x\,$ as $cos⁡(2x+x)\cos(2x + x)$ , show that $cos 3x = 4\cos^3 x - 3\cos x$

[2]

b.

Solve, for $\leq x \leq \pi$ , the equation,

4\cos^3 x - 3\cos x = \frac{\sqrt{3}}{2}

Give your answers in terms of $π\pi$ .

[4]

a.

By writing $\cos 3x\,$ as $cos⁡(2x+x)\cos(2x + x)$ , show that $cos 3x = 4\cos^3 x - 3\cos x$

[2]

b.

Solve, for $\leq x \leq \pi$ , the equation,

4\cos^3 x - 3\cos x = \frac{\sqrt{3}}{2}

Give your answers in terms of $π\pi$ .

[4]

3.4 Trigonometry (A-level only) Questions