Find the derivative of `y=sqrt(x^2+1)`.

Explanation

Here `y = f(g(x))`, where `f(u) = sqrt(u)` and `u = g(x) = x^(2) + 1`. Since the derivatives of f and g are
`f'(u) = 1/(2sqrt(u) and g'(x) = 2x`,
the chain Rule gives
`(dy)/(dx) = d/(dx) f(g(x)) = f' (g(x)). G'(x) =`
`1/(2sqrt(g(x))) cdpt g'(x) = 1/ (2sqrt(x^2 + 1)) cdot 2(x) = x/(sqrt(x^2 + 1))`