Answer
The key to determining the area of a triangle using Heron's formula is knowing the lengths of all three sides, denoted as a, b, and c. The formula involves calculating the semi-perimeter (s) of the triangle: s = (a + b + c) / 2. With this value, the area (A) of the triangle can be determined: A = √(s(s - a)(s - b)(s - c)).