Question 928620
Solve the following equation in the interval [0, 2pi]. 
2(cos(t))^2-cos(t)-1=0. 
(2cos(t)+1)(cos(t)-1)=0
..
2cos(t)+1=0
cos(t)=-1/2
t=2π/3, 4π/3
..
cos(t)-1=0
cos(t)=1
t=0, 2π