Prove that these are equal using Trig identities
Remember that \(\cos^2x+\sin^2x=1\)
Rearrange this in the form: \(\sin^2x=1-\cos^2x\)
Substitute this into the left hand side (LHS) of your identity:
LHS: \(1-\cos^2x-cos^2x\)
Simplify
LHS: \(1-2\cos^2x\)
So LHS = RHS
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