Question

Find the value of $\sin (-{210}^{\circ })$

Answer 1

$\sin (-{210}^{\circ })$

$=-\sin \left({210}^{\circ }\right)$ since $\sin (-\theta )=-\sin \theta$

$=-\sin ({180}^{\circ }+{30}^{\circ })$

$=-(-\sin {30}^{\circ })$ since $\sin (180+\theta )=-\sin \theta$

$=\sin {30}^{\circ }$

$=\frac{1}{2}$