solve for 0< x <(or equal to) 2pie: sinx=cos2x ?

Answer 1

sin(x) = cos(2x)
sin(x) = cos²(x) - sin²(x)
sin(x) = 1 – 2*sin²(x)
2 sin²(x) + sin(x) – 1 = 0
This quadratic equation has two solutions:
sin(x) = 0.5
and
sin(x) = -1.
Corresponding angles are:
x = 30°,
x = 150°, and
x = 270°.
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