What is exactly meant by
angle subtended by all sides of a polygon at its center
I encountered these while solving this problem:
How can we determine the number of sides of a polygon, given the angles subtended by all the side at its center are equal to $72 ^\circ$?
Could somebody please explain (with a figure) what is meant to calculate in this question?
Edit: I tried to Google some help, which took me to this page.I think this is what meant in this question.If so why all sides is mention in this question? and why it is supposed that the polygon will have equal sides?