# trig

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How do you express in terms of angles less than 90 degrees?

sin 120 degrees
cos 150 degrees
tan 280 degrees

• trig -

1. What quadrant is the angle in? That determines the ± according to the CAST rul
2. "How far is it to the x-axis"?

sin 120° = sin60
cos150° = -cos 30
tan 280° = -tan 80°

• trig -

Sin (180 - A) = sin A. (angle in degrees)
sin 120 = sin (180 - 60) = sin 60

Cos (180 - A) = - cos A
cos 150 = cos (180 - 30) = - cos 30

tan (360 - A) = - tan A,
tan 280 = tan (360 - 80) = - tan 80

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