Law of Tangents/Corollary/Also presented as

Corollary to the Law of Tangents: Also presented as
The Corollary to the Law of Tangents can also be found presented as:
 * $\dfrac {a - b} {a + b} = \tan \dfrac {A - B} 2 \tan \dfrac C 2$

or:
 * $\dfrac {a - b} {a + b} \cot \dfrac C 2 = \tan \dfrac {A - B} 2$