prove that sin^4A-cos^4A=1-2cos^2A
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Answer:
Step-by-step explanation:
Given that:-sin^4A-cos^4A=1-2cos^2A
LHS=(sin^2A)^2-(cos^2A)^2
=(sin^2A+cos^2A)(sin^2A-cos^2A)
=1(sin^2A-cos^2A)
=(1-cos^2A)-cos^2A
=1-cos^2A-cos^2A
=1-2cos^A=RHS
PROVED
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