# Constant multiple rule for derivatives

Let $f$ and $g$ be differentiable functions and $c$ a constant. Then the following formula holds: $$\dfrac{\mathrm{d}}{\mathrm{d}x} \left[cf(x) \right] = c f'(x),$$ where $\dfrac{\mathrm{d}}{\mathrm{d}x}$ denotes the derivative operator.
1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $3.3.1$