How do you use the angle sum identity to find the exact value of #sin285#?
1 Answer
Oct 25, 2016
Explanation:
Trig unit circle -->
sin 285 = sin (-75 + 360) = sin (-75)
Property of complementary arcs -->
sin (-75) = sin (-15 + 90) = - cos 15
Next, find (cos 15) by using trig identity:
Since cos 15 is positive then take the positive value only.
Finally:
sin 285 = - cos 15 =
Check by calculator:
sin 285 = - 0.965