## Precalculus (10th Edition)

As we know the sum of the $3$ angles is $180^o$ so find the measure of the third angle by subtracting the known two angles from $180^o$. Then by the Law of Sines $\left(\dfrac{{\sin {A}}}{a} = \dfrac{{\sin {B}}}{b} = \dfrac{{\sin {C}}}{c}\right)$ I can get the other two sides. e.g. if $a$ is known and I have the $3$ angles then $b=a\frac{{\sin {B}}}{\sin {A}}, c=a\frac{{\sin {C}}}{\sin {A}}$.