## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

By Heron's formula, the area of a triangle with sides $a,b$ and $c$ is given by: $K=\sqrt{s(s-a)(s-b)(s-c)}$; where $s=\dfrac{a+b+c}{2}$ This formula is used for computing the area of a triangle when the sides are known. Therefore, the statement is true.