Solve: $\displaystyle 4 cos^2 x = 3$

for

0 < x < 2pi

I thought the way I did it was right but I get the wrong answer.

so I factored

cosx(4cosx)=3

so

cosx=3 and 4cosx=3

cosx cannot =3 so 4cosx=3 ....

cosx=3/4

so I sketch a little graph and find x=pi/6 and 15 pi/8? but this gets confusing. whats the right way to find this?

but that isnt right, could someone help me with this question?

thanks.