#### Answer

$h=r\cos\theta$

#### Work Step by Step

In a right angled triangle, $\cos\theta=\frac{base}{hypotenuse}$
Since $r=hypotenuse$ and $h=base$, the formula becomes:
$\cos\theta=\frac{base}{hypotenuse}=\frac{h}{r}$
Solving for $h$:
$h=r\cos\theta$