设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(11t^2)设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(1-t^2)

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设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(11t^2)设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),co

设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(11t^2)设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(1-t^2)
设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(11t^2)
设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(1-t^2)

设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(11t^2)设tan(θ/2)=t,求证:sinθ=2t/(1+t^2),cosθ=(1-t^2)/(1+t^2),tanθ=2t/(1-t^2)
sinθ=2sinθ/2*cosθ/2
=2tanθ/2*cosθ/2*cosθ/2
=2tanθ/2(cosθ/2)^2
=2t*(cosθ/2)^2
而(cosθ/2)^2
=1/(secθ/2)^2
=1/[1+(tanθ/2)^2]
=1/1+t^2
所以sinθ=2t/(1+t^2)
同理
cosθ=2(cosθ/2)^2-1
=2/1+t^2-1
=(1-t^2)/(1+t^2)
tanθ=sinθ/cosθ=2t/(1-t^2)