How do you find the value of $sin (- 120)$ $sin (-120)$ ?

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Answer 1 · 2015-10-20T18:34:11

$sin (- 120^{\circ}) = - \frac{\sqrt{3}}{2}$ $sin(-120^@) = -sqrt(3)/2$

$120^{\circ}$ $120^@$ is equivalent to a reference angle of $60^{\circ}$ $60^@$ in Quadrant III

$sin (60^{\circ}) = \frac{\sqrt{3}}{2}$ $sin(60^@) = sqrt(3)/2$
but in Quandrant III the $sin$ $sin$ is negative (using CAST notation)

so $sin (- 120^{\circ}) = - \frac{\sqrt{3}}{2}$ $sin(-120^@) = -sqrt(3)/2$

How do you find the value of sin(−120)sin (-120) ?