Question

How do you prove `sin x = 1 - 2 cos^2x`?

Answer 1

For `x=pi/6`:
`sin(x) = 1/2, cos(x) = sqrt(3)/2`
`1 - 2 * (sqrt(3)/2)^2 = 1-2*3/4 = 1-3/2 = -1/2 != 1/2`//

Which proves it is False