求In(secx+tanx)的导数?

ln(secx+tanx)=ln(1/cosx+sinx/cosx)=ln[(sinx+1)/cosx]所以In(secx+tanx)的导数=1/(sinx+1)/cosx * [(sinx+1)/cosx]'=cosx/(sinx+1)*[cosx*cosx-(sinx+1)*(-sinx)]/cos^2x=cosx/(sinx+1)*(cos^2x +sin^2x+sinx)/cos^2x=cosx/(sinx+1)*(1+sinx)/cos^2x=1/cosx