# What is the derivative of 2cos*x?

$\frac{d}{\mathrm{dx}} \left(2 \cos x\right) = - 2 \sin x$
$\frac{d}{\mathrm{dx}} \left(2 \cos x\right) = 2 \frac{d}{\mathrm{dx}} \left(\cos x\right)$
$= 2 \left(- \sin x\right)$
$= - 2 \sin x$