Heron's Formula
When given three sides of a triangle \(\; a,\ b, \ c\).
The area \(\;A\;\) of the triangle is given by:
Perimeter formula
\(p = a+b+c \)
Semiperimeter: \(\; s \equiv \frac{1}{2} p \)
Area formula
\(A= \sqrt { s(s-a)(s-b)(s-c) } \)
Semiperimeter: \(\; s \equiv \frac{1}{2} (a+b+c) \)