Question 261494
For any angle not between 0 and 90, you use what's called a reference angle. The reference angle is always the angle between the terminal side of the angle and the x-axis.<br>
So in your case, using the angle between the terminal side of 120 and the x-axis, the reference angle is 60. Here's an illustration:
{{{drawing(400, 400, -1, 1, -1, 1, grid(1), line(0, 0, -0.5, sqrt(3)/2), line(-0.5, 0, -0.5, sqrt(3)/2), locate(0, 0.1, 120), locate(-0.2, 0.1, 60))}}}