已知2θ=根号2/3 则sin4次方θ-cos4次方θ=

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已知2θ=根号2/3 则sin4次方θ-cos4次方θ=
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已知2θ=根号2/3 则sin4次方θ-cos4次方θ=
已知2θ=根号2/3 则sin4次方θ-cos4次方θ=

已知2θ=根号2/3 则sin4次方θ-cos4次方θ=
cos2θ=根号2/3
sin4次方θ-cos4次方θ
=(sin²θ+cos²θ)(sin²θ-cos²θ)
=-cos2θ
=-根号2/3

sin^4 θ-cos^4 θ
=(sin^2 θ-cos^2 θ)(sin^2 θ+cos^2 θ)
=sin^2 θ-cos^2 θ
=-cos2θ
?

sin4次方θ-cos4次方θ
=(sin^2θ-cos^2θ)(sin^2θ+cos^2θ)
=sin^2θ-cos^2θ
=-cos2θ cos2θ=根号2/3
=-根号2/3