# Second derivative rule for parametric descriptions

Consider a parametric description of the form $x = f(t), y = g(t)$, where $f$ and $g$ are functions of one variable. The second derivative rule states that:
$\frac{d^2y}{dx^2} = \frac{f'(t)g''(t) - g'(t)f''(t)}{(f'(t))^3}$