\(\large{ A= \sqrt { s\;(s-a)(s-b)(s-c) } }\)
\(\large{ s \equiv \frac{1}{2} \;(a+b+c) }\) (semiperimeter)
\(\large{ p = a+b+c }\)
\(\large{ s \equiv \frac{1}{2}\; p }\) (semiperimeter)