cosα*根号[（1-sinα）/（1+sinα）]+sinα*根号[（1-cosα）/（1+cosα）]
=cosα*根号[(1-sinα)^2/(1-sin^2α)]+sinα*根号[(1-cosα)^2/(1-cos^2α)]
=cosα*(1-sinα)/cosα+sinα*(1-cosα)/sinα
=(1-sinα)+(1-cosα)
=2-sinα-cosα