数学0011

1.[ sin2α/(1+cos2α) ]* [cosα/(1+cosα)]
=[2sinαcosα/(2cosαcosα)]*[cosα/(1+cosα)]
=sinα/(1+cosα)=tan(α/2)
2.设t=sinαcosα
平方得1-2t=t^2
(t-1)^2=2
t=√2-1
sin2α=2t=2√2-2

1、最后化简结果是tana/2
所用到的公式sin2a=2sinacosa
cos2a=2cos^2a-1
2、化简后a=π/4 sin2a=1