Differential equation problem in Maple I have differential equation $x\cdot\sqrt{4+y^2}\,dx + y\cdot\sqrt{1+x^2}\,dy = 0$, which is simple to solve on paper, but I have problem solving it with Maple (I use 10th, tried on 14th also). When applying dsolve it complains that it is not ODE.
Any suggestions?
Thank you in advance

The command you are looking for is 
dsolve(x*sqrt(4+y(x)^2)+y(x)*sqrt(1+x^2)*diff(y(x),x), y(x)).
