Following the notations of figure $1\mathrm{.}9,$ find the angle for which:

$a=3,b=5$

$a=3,b=-5$

$a=-3,b=-5$

$a=-3,b=5$

In the following first draft $($not to scale$),$ the designer included various requirements of a building code. Now, more details of some elements have to be figured out. Calculate the lengths of $a,b,$ and $c,$ and the size of $.$