Answer
Use the formula $K=\sqrt{s(s-a)(s-b)(s-c)}$, where $s=\frac{a+b+c}{2}$.
Work Step by Step
We know that by Heron's theorem $K=\sqrt{s(s-a)(s-b)(s-c)}$, where $s=\frac{a+b+c}{2}$ and $a$, $b$ and $c$ are the sides of the triangle and $K$ is the area of the triangle.
Hence, to find the area of a triangle where the lengths of three sides are given, I simply use the formula above.
