Question 640630
I'm going to use x in place of theta (it's easier to type)


4cos(x)=1+2cos(x) 


4cos(x)-2cos(x) = 1


2cos(x) = 1


cos(x) = 1/2


x = arccos(1/2)


x = pi/3 or x = -pi/3


x = pi/3 or x = -pi/3+2pi


x = pi/3 or x = -pi/3+6pi/3


x = pi/3 or x = 5pi/3