Question

Calculate the value of the expression: $\sin (-{120}^o)$.

• A. $-\frac{\sqrt{3}}{2}$
• B. $-\frac{\sqrt{1}}{2}$
• C. $-\frac{\sqrt{5}}{2}$
• D. $-\frac{\sqrt{-1}}{2}$

Answer 1

Answer: (A)

$-\frac{\sqrt{3}}{2}$

$\sin (-{120}^o$) = $-\frac{\sqrt{3}}{2}$

The angle $-{120}^o$ is coterminal with ${240}^o$.

Therefore, the value of $\sin (-{120}^o)$ = $-\frac{\sqrt{3}}{2}$.

So, option A is correct.