sin^6 a+cos^6 a+3×sin^2 a×cos^2 a=?

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sin^6 a+cos^6 a+3×sin^2 a×cos^2 a=?

sin^6 a cos^6 a 3sin^2 acos^2a
=(sin^2 a cos^2 a)(sin^4 a cos^4 a-sin^2 acos^2 a)
3sin^2 acos^2a
=sin^4 a cos^4 a-sin^2 acos^2 a 3sin^2 acos^2a
=sin^4 a cos^4 a 2sin^2 acos^2 a
=(sin^2 a cos^2 a)^2
=1