若sin2a=根号2/2,则sin^4a+cos^4a,

若sin2a=根号2/2,则sin^4a+cos^4a,
若sin2a=根号2/2,则sin^4a+cos^4a,

若sin2a=根号2/2,则sin^4a+cos^4a,
sin^4a+cos^4a
=(sin²a+cos²a)²-2sin²acos²a
=1-1/2(2sinacosa)²
=1-1/2sin²2a
=1-1/2(√2/2)²
=1-1/2*1/2
=1-1/4
=3/4