solve equation exactly over interval (0, 2ð)

Question

sin(x)= 1-2sin^2(x)

Answer 1

change sin(x) to u.

u=1-2u^2
2u^2+u-1=0
(2u-1)(u+1)=0
u= 1/2 or -1

sin(x)=1/2 or sinx=-1
now solve.