Cos(theta)=-1/2

Question

What is theta in terms of pi 

Answer 1

Hi Blaine,

cos(theta)=-1/2  for theta between 0 and 2pi

there are two possibilities

2pi/3 

4pi/3

because cos is negative in both quadrant II and III

and the angles that give -1/2 in those two  quadrant are the ones I mentioned