It is very easy!! We apply the process by which there is calculated the value of a directly proportional magnitude to other one, ie, we use a rule of three direct.

We know that the volume of a sphere is: . So, we have the following:

360º
                                         ⇒    x=   
x          nº



being n º the number of degrees that the wedge includes and x the volume that we want to calculate (the mystery).