If $y = \log x$, what is $\frac{d^2y}{dx^2}$?

Explanation

1. 01

   First derivative: $\frac{dy}{dx} = \frac{1}{x}$.

2. 02

   Differentiate again: $\frac{d^2y}{dx^2} = - \frac{1}{x^{2}}$.