若cos2θ=-3/4,则sin^4θ+cos^4θ=
问题描述:
若cos2θ=-3/4,则sin^4θ+cos^4θ=
答
cos2θ=2(cosθ)^2-1=-3/4
(cosθ)^2=1/8 (sinθ)^2=7/8
sin^4θ+cos^4θ=(7/8)^2+(1/8)^2=25/32
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