Differentiate: .\(\displaystyle \L\frac{dy}{dx}\:=\:\frac{(1\,+\,x^2)\cdot2x\,-\,x^2\cdot2x}{(1\,+\,x^2)^2}\:=\:\frac{2x\,+\,2x^3\,-\,2x^3}{(1\,+\,x^2)^2}\:=\:\frac{2x}{(1\,+\,x^2)^2}\)If \(\displaystyle y\:=\:\frac{x^2}{1\,+\,x^2}\), find \(\displaystyle dy\).