已知sin∧4θ+cos∧4θ=5/9,求sin2θ
问题描述:
已知sin∧4θ+cos∧4θ=5/9,求sin2θ
答
sin∧4θ+cos∧4θ=5/9
(sin^2θ+cos^2θ)^2-2(sincosθ)^2=5/9
1-1/2*(sin2θ)^2=5/9
(sin2θ)^2=8/9
sin2θ=正负2根2/3