SOLUTION: Solve the equation on interval [0,2pi). Give answer in radicals and type exact answer using pi as needed. 8cos^2x-4=0 I know you have to factor the equation but I got stuck

Algebra ->  Trigonometry-basics -> SOLUTION: Solve the equation on interval [0,2pi). Give answer in radicals and type exact answer using pi as needed. 8cos^2x-4=0 I know you have to factor the equation but I got stuck      Log On


   

Question 868053: Solve the equation on interval [0,2pi). Give answer in radicals and type exact answer using pi as needed.
8cos^2x-4=0

I know you have to factor the equation but I got stuck trying to do that
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
8cos%5E2%28x%29-4=0
cos%5E2%28x%29-1%2F2=0
%28cos%28x%29-1%2Fsqrt%282%29%29%28cos%28x%29%2B1%2Fsqrt%282%29%29=0
%28cos%28x%29-sqrt%282%29%2F2%29%28cos%28x%29%2Bsqrt%282%29%2F2%29=0
Two solutions:
cos%28x%29-sqrt%282%29%2F2=0
cos%28x%29=sqrt%282%29%2F2
x=pi%2F4 and x=%287%2F4%29pi
and
cos%28x%29%2Bsqrt%282%29%2F2=0
cos%28x%29=-sqrt%282%29%2F2
x=%283%2F4%29pi and x=%285%2F4%29pi