How do you solve the trigonomic equation sin2x equals negative cosx?

Answer 1

Sin(2x) = -cos(x)

But sin(2x) = 2 sin(x) cos(x)

Substitute it:

2 sin(x) cos(x) = -cos(x)

Divide each side by cos(x):

2 sin(x) = -1

sin(x) = -1/2

x = 210°

x = 330°