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Question
Show that none of the following is an identity:
`cos^2theta + cos theta = 1`
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Solution
`cos^2theta + cos theta =1`
LHS = `cos^2 theta + cos theta`
=`1- sin^2 theta + cos theta `
=` 1- ( sin^2 theta - cos theta )`
Since LHS ≠ RHS, this not an identity.
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