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Solving trigonometric identities.

Solve for x:

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

b) sin2x=cosx

c) sin2x=2sinx

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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