How to find radius with diameter. Where r is the radius of the circle and p is a constant estimated to be 3142. For example if the radius is 5 inches then using the first area formula calculate p x 5 2 314159 x 25 7854 sq in.
For example if the radius of the circle is 6 inches first you would square 6 and get 36.
Watch this tutorial to see how its done. Area of an arch given height and radius. You cannot find the area of a sector if you do not know the radius of the circle. So now if you know the width of the circle otherwise called the diameter you can simply divide it by 2 to get the radius.