A full circle in radians is 2π, and in degrees it's 360°. I want to convert the 72° to radians:
72° in radians = 72/360 * 2π = 2/5π
The circumference of a full circle is the number of radians times the radius. (ie., 2πr), so the JK part of the circle is:
5* 2/5π simplifies to 2π
The easiest way is just to plug it in to your calculator. you find the square root button and plug the number in. for example if you plug in the square root of 289 you get 17
