2pi radians in a circle
1 circle=360
therefor
ratio and proporiton
parts/whole=130/360=xradians/2pi
130/360=xradians/2pi
13/36=xradians/2pi
times 72pi both sides
26pi=36xradians
divide both sides by 36
(13pi)/18=xradians
(13pi)/18 radians
aprox 2.2689280275927 radians
