TRIG help quickly please
posted by Greg on .
Mark any solutions to the equation 2cos2x  1 = 0. The answer can be more than one. Thank you
π/8
7π/4
15π/4
3π/4

2 cos (2x)  1 = 0
cos (2x) = 1/2
2x = π/3 or 2x = 2ππ/3 or 5π/3
x = π/6 or x = 5π/6
none of the given answers apply
I will assume you meant
2 cos^2 x  1 = 0
by definition:
2cos^2 x 1 = cos (2x)
so cos(2x) = 0
2x = π/2 or 2x = 3π/2
x = π/4 or x = 3π/4
I see one of those answers. 3π/4
looking at the others, note that 7π/4 is coterminal with π/4
so it would be a solution as well