How do you calculate $sin (-150°)$ ?

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Answer 1 · 2018-07-21T14:37:02

$-1/2$

$\sin(-150^\circ)$

$=-\sin(150^\circ)$

$=-\sin(180^\circ-30^\circ)$

$=-\sin(30^\circ)\quad (\because \ \sin(180^\circ-\theta)=\sin\theta)$

$=-1/2$

Answer 2 · 2018-07-21T15:33:30

$-1/2$

Recall the negative angle identity

$sin(-theta)=-sin(theta)$

With this in mind, we can rewrite $sin(-150)$ as $-sin(150)$ .

$150^@$ has a reference angle of $30^@$ , which means it will have the same trig values as $30^@$ .

On the Unit Circle, we know the coordinates for $30^@$ are $(sqrt3/2,1/2)$ , where the $y$ -coordinate is the $sin$ value.

This means $sin(-150)=-1/2$

Hope this helps!

How do you calculate sin (-150°)sin (-150°)?