Trigonometric Identities (Grade 11 NSC Matric Mathematics): Quizzes

An equation true for all valid values

$\tan \theta = \frac{\sin \theta}{\cos \theta}$

When $\cos \theta = 0$

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

Pythagorean theorem

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

Convert everything to sine and cosine

$\sin^2 \theta$

$1$

Replace $1$ with $\sin^2 \theta + \cos^2 \theta$