The area of the circle formula can be visually proven by dividing the area into concentric rings. Unwrapping the rings and placing them next together forms the shape of a triangle. As the number of rings approaches infinity their area approaches the area of the triangle with the base of and a height of .

This is shown in the series of illustrations below:

As the number of rings approaches infinity, the shape on the right-hand side approaches the shape of a triangle.

Recall that the area of a triangle is given by the formula:

Then, we can substitute the length of the base and height into the formula. The base is equal to the circumference of the circle which is given by the circle constant multiplied by the radius . The height is equal to the radius of the circle. This visual proof gives us the area of the circle formula.