What are the exact values of (listed below)?

Question

cos(-120)

sin(-225)

Sin 495

cosec 300

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Answer 1 · 2018-06-27T12:34:31

See explanation below

In goniometric circle we can realize that

$cos (- 120) = sin 30 = \frac{\sqrt{3}}{2}$ $cos(-120)=sin30=sqrt3/2$

$sin (- 225) = sin 135 = sin 45 = \frac{\sqrt{2}}{2}$ $sin(-225)=sin135=sin45=sqrt2/2$

$sin 495 = sin (495 - 360) = sin 135 = \frac{\sqrt{2}}{2}$ $sin495=sin(495-360)=sin135=sqrt2/2$

$cos e c 300 = \frac{1}{sin 300} = \frac{1}{- sin 30} = - 2$ $cosec300=1/sin300=1/-sin30=-2$