已知2θ=根号2/3 则sin4次方θ-cos4次方θ=
问题描述:
已知2θ=根号2/3 则sin4次方θ-cos4次方θ=
答
cos2θ=根号2/3
sin4次方θ-cos4次方θ
=(sin²θ+cos²θ)(sin²θ-cos²θ)
=-cos2θ
=-根号2/3