证明(1+secx+tanx)/(1+secx-tanx)=(1+sinx)/cosx
问题描述:
证明(1+secx+tanx)/(1+secx-tanx)=(1+sinx)/cosx
答
左=(cosx+1+sinx)/(cosx+1-sinx).右=(1+sinx)/cosx.
交叉相乘
(cosx+1+sinx)cosx=cos²x+cosx+sinxcosx.
(1+sinx)(cosx+1-sinx)=cosx+1-sinx+sinxcosx+sinx-sin²x
=cos²x+cosx+sinxcosx.
所以 :(1+secx+tanx)/(1+secx-tanx)=(1+sinx)/cosx.
答
左边=(cosx/cosx+1/cosx+sinx/cosx)/(cosx/cosx+1/cosx-sinx/cosx)=(cosx+1+sinx)/(cosx+1-sinx)=(cosx+1+sinx)^2/[(cosx+1+sinx)(cosx+1-sinx)]=(cos²x+sin²x+2*sinx*cosx+2*cosx+2*sinx+1)/(cos²...