 Let the circumference of a circle be measured in degrees and let the radius "R" of the circle be also measured in degrees.Choosing a fixed diameter "AB" and an arbitrary point "P" on the circle and dropping the perpendicular "PM" to "AB", we can compute the area of the triangle "APB" in two ways.Equating the two expressions for the area one gets (1/2) "AB" × "PM" = (1/2) "AP" × "BP".