# Solving Trigonometric Identities on an Interval

Find all solutions in the interval [0,2pi):

cos2x + 5cosx = 2

https://brainmass.com/math/trigonometry/solving-trigonometric-identities-interval-104882

#### Solution Preview

We have the equation cos2x + 5cosx = 2

We use the identity cos2x=2(cosx)^2-1 here.

Then the equation becomes

2(cosx)^2-1+ 5cosx = 2==>2(cosx)^2+5cosx-3=0.

Observe that 2 x (-3)=-6. Write -6 as product of two ...

#### Solution Summary

Solving Trigonometric Identities on an Interval is investigated.

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