sin^2α*tanα+cos^2α*cotα+2sinα*cosα =sin^3α/cosα+cos^3α/sinα+2sinα*cosα =(sin^4α+cos^4α+2sin^2αcos^2α)/(sinα*cosα )=(sin^2α+cos^2α)^2/(sinα*cosα )=1/(sinα*cosα )=2/sin2α答案好像有点问题诶..