posted by Anonymous .
Find all solutions to 2 cos(theta) = - 1 on the interval 0 less than or equal to theta less than 2 pi
Give your answers as exact values, as a list separated by commas.
cosine is negative in II or III
and I know cos 60° = cosØ/3 = 1/2
so for your cosØ = -1/2
Ø = 180-60 =120° or Ø = 180+60 = 240°
Ø = 2π/3 or Ø = 4π/3