Find the area of a triangle whose two side lengths are cm and cm, and the angle included
between them is .
The cosine rule states that , where , , and are the side lengths of a triangle, and is the angle opposite the side of length . Find the approximate length, , of the third side of the triangle as follows:
According to Heron's formula, the area of a triangle whose side lengths are , , and is equal to , where is half the triangle's perimeter. The perimeter of the triangle is approximately , so is equal to approximately . Find the approximate area of the triangle using Heron's formula.
Thus, the approximate area of the triangle is .