# Solving trigonometric identities.

Solve for x:

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

b) sin2x=cosx

c) sin2x=2sinx

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#### Solution Preview

a) Note that sin(^2)x = 1-cos(^2)x

So the equation is

1-cos(^2)x=cosx-1

cos(^2)x+cosx-2=0

Let y=cosx

Then we need to solve y^2+y-2=0

y=(-1+sqrt(1-(-2*4)))/2 and

y=(-1-sqrt(1-(-2*4)))/2

So ...

#### Solution Summary

Trigonometric identities are solved.

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