Question

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

Answer 1

Answer:

Step-by-step 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