Question

What does 2π/3 equal and cos2π/3 equal?

Answer 1

Explanation:

2π/3 radians is equivalent to

2π 180°

-------- * ---------- = 120°

3 π rad

This angle (120°) is 30° past 90°. The 'opposite side' of the triangle formed by this ray of length 1 is √3 and the 'adjacent side' is 1.

adj side -1

cos 120° is in Quadrant II. cos 120° = --------------- = ---------

hyp 2

√3

and sin 120° = --------

2