# What is the integral of 9sinx?

Apr 28, 2017

$- 9 \cos x$

#### Explanation:

If $f \left(x\right) = \cos x$
Then by the differential rule
$f ' \left(x\right) = - \sin x$
So I make a new function called $g \left(x\right) = - \cos x$
by the same rule
$g ' \left(x\right) = \sin x$