Double Angle Formulae (Leaving Cert Mathematics): Quizzes

$\sin(2\theta) = 2\sin(\theta)\cos(\theta)$

$\cos(2\theta) = \cos^2(\theta) - \sin^2(\theta)$

$\cos(2\theta) = 1 - 2\sin^2(\theta)$

$\tan(2\theta) = \frac{2\tan(\theta)}{1 - \tan^2(\theta)}$

Three

$\frac{24}{25}$

$\frac{-119}{169}$

$\theta = 22.5°$ and $\theta = 112.5°$

$\sin^2(\theta) + \cos^2(\theta) = 1$

Sine sum identity

Physics

Dividing loses solutions where $\cos x = 0$