Find the principal root(s) for each question

Question

^{4cos^2x-1=0}

Answer 1

4cos^2x-1=0

4cos^2x=1

cos^2x=1/4

take the square root of both sides

cosx=±√(1/4)

cosx=1/2 or cosx=-1/2

cos is equal to 1/2 at 30º and at 300º

cos is equal to -1/2 at 120º and at 240º

the principal root is defined in algebra as the positive square root, so if you only want to use 1/2, then you have

30º and 300º