
已知cos2θ=3/5,求sin^4θ+cos^4θ的值。谢谢啦!
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sin^4θ+cos^4θ
=(sin^2θ+cos^2θ)^2-2sin^2θcos^2θ
=1-1/2sin^2(2θ)
=1-1/2(1-cos^2(2θ))
=17/25
=(sin^2θ+cos^2θ)^2-2sin^2θcos^2θ
=1-1/2sin^2(2θ)
=1-1/2(1-cos^2(2θ))
=17/25
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