Problem - 2628
What is Heron's formula to calculate a triangle's area given the lengths of three sides?
Let the three sides be $a$, $b$ and $c$. Then the area $S$ can be expressed as $$S=\sqrt{p(p-a)(p-b)(p-c}$$ where $p = \frac{1}{2}\cdot(a+b+c)$.