若sin2a=根号2/2,则sin^4a+cos^4a,
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![若sin2a=根号2/2,则sin^4a+cos^4a,](/uploads/image/z/15210805-13-5.jpg?t=%E8%8B%A5sin2a%3D%E6%A0%B9%E5%8F%B72%2F2%2C%E5%88%99sin%5E4a%2Bcos%5E4a%2C)
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