Determine the area of the figure below using Heron's formula.
The figure is composed of a square and a right-angled triangle. The right-angled triangle has sides measuring 21 cm, , and 35 cm. 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 right-angled triangle is , so is equal to . Find the area of the right-angled triangle using Heron's formula.
The square has a side length of 21 cm, so its area is . Therefore, the area of the figure is .