## Trigonometry 7th Edition

$c=22.5$
$a^{2}+b^{2}=c^{2}$ $13.5^{2}+18^{2}=c^{2}$ The number is 18 as the roof has two sides and we are simply trying to find one side. Finding one side forms a right angled triangle which we can use trig on, this splits the original 36 in half. $182.25+324=c^{2}$ $506.25=c^{2}$ $c=22.5$