Solve the following differential equation: `e^xtany\ dx+(1-e^x)sec^2y\ dy=0`

Explanation

`e^(x)tanydx+(1-e^(x))sec^(2)ydy=0`
or `(1-e^(x))sec^(2)ydy=-e^(x)tanydx`
or `int(sec^(2)y)(tany)dy=int(-e^(x))/(1-e^(x))`dx
or `log(tany)=log(1-e^(x))+logC`
or `log(tany)=log[C(1-e^(x))]`
or `tany=C(1-e^(x))`