Strategy for Further Trigonometric Equations (Edexcel A-Level Mathematics): Quizzes

$2\sin \theta \cos \theta$

$2\sin \theta \cos \theta$

$\frac{1}{2}[\cos(A - B) - \cos(A + B)]$

Let $u = \sin \theta$ or $\cos \theta$

Trigonometric functions are periodic

$\theta = \theta_0 + 180^\circ n$

$\theta = \theta_0 + 360^\circ n$

To check for extraneous solutions

$\sqrt{a^2 + b^2}$

$\frac{b}{a}$