Originally Posted by

**andy000** Hi,

the question I have been working on is cos(x -2pi/3) = 1/2 -2pi<x<2pi

I know from one of the special triangles that cos(pi/3) = 1/2 = cos(x-2pi/3)

so cos(x-2pi/3) = cos(pi/3), cos(-pi/3), cos(5pi/3), cos(-5pi/3), cos(7pi/3), cos(-7pi/3)

if this is right, should I just solve for each of them eg:

if cos(x-2pi/3) = cos(pi/3) ==> x-2pi/3 = pi/3 ==> x = 2pi/3+ pi/3 ==> x = pi

It would also be good if someone could let me know if I have missed any angles that give cos()= 1/2

thanks