can you solve this ? $ y'= \frac{x\sqrt{1+y^2}} { y\sqrt{1+x^2}} $

Question

thanks, hard to write with keyboard $$ y'= \frac{x\sqrt{1+y^2}} { y\sqrt{1+x^2}} $$ i dont know what i start with

Answer 1

$$ \frac{ydy}{xdx}= \frac{\sqrt{1+y^2}}{\sqrt{1+x^2}}\leadsto \\ \frac{d(1+y^2)}{\sqrt{1+y^2}}= \frac{d(1+x^2)}{\sqrt{1+x^2}} \leadsto \\ \sqrt{1+y^2}=c+ \sqrt{1+x^2}. $$