Law of Tangents/Corollary/Examples/Arbitrary Example 1

Example of Use of Corollary to Law of Tangents
Let $\triangle ABC$ be a triangle whose sides $a, b, c$ are such that $a$ is opposite $A$, $b$ is opposite $B$ and $c$ is opposite $C$.

Let $\triangle ABC$ be such that:

where the units of measurement of $a$ and $b$ are arbitrary.

Then:

Proof
First:

Then:

Then we have: