Question

设y=ln(x/1+x)-cot2x,求dy.

Answer 1

y=ln(x/(1+x))-cot2x

dy = [(1+x)/x] d(x/(1+x)) + (csc2x)^2 .d(2x)

= { (1+x)/[x(1+x)^2] + 2(csc2x)^2 }dx