Sin4A+cos4
A+2sin2A cos 2A
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LHS = sin^4A + cos^4A + 2sin^2A.cos^2A
= (sin^2A)^2+(cos^2A)^2+2sin^2A.cos^2A =[(sin^2A+cos^2A)^2−2sin^2A.cos^2A]+2sin^2A.cos^2A
°.° [a^2+b^2=(a+b)^2−2ab]
=[1^2−2sin^2A cos^2A]+2sin^2A.cos^2A °.°(sin^2A+cos^2A=1)
=1−2 sin^2A cos^2A+2sin^2A.cos^2A
= 1-0
=1
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