Double Angle Formulae (Leaving Cert Mathematics): Flashcards

Trig functions of $2\theta$ in terms of $\theta$

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

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

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

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

Three

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

Sine sum identity

Pythagorean: $\sin^2\theta + \cos^2\theta = 1$

Simplifying, solving equations, calculus, physics

May lose solutions

Factor common terms