cos^4a+ sin^4a= 1-2cos^2sin^2
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lhs=cos⁴a+sin⁴a=(cos²a)²+(sin²A)²
=using a²+b²=(a+b)²-2ab
=(sin²a+cos²a)-2sin²a.cos²a
we know that:sin²a+cos²a=1
=1-2sin²a.cos²a
..................................proved.................................................. please mark me brainliest
=using a²+b²=(a+b)²-2ab
=(sin²a+cos²a)-2sin²a.cos²a
we know that:sin²a+cos²a=1
=1-2sin²a.cos²a
..................................proved.................................................. please mark me brainliest
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