若2sin(π/4+a)=sinθ+cosθ,2sin^2β=sin2θ,求证sin2a+(1/2)cos2β=0
人气:413 ℃ 时间:2020-05-06 08:06:36
解答
2sin(π/4+α)=√2(sina+cosa)√2(sina+cosa)=sinθ+cosθ 将这个式子平方,得2(1+sin2a)=1+sin2θ 2sin2β=sin2θ2(1+sin2a)=1+2sin2β2+2sin2a=1+2sin2βsin2α+1=2sin2β所以(sin2α+1)/2sin2β=1...
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