we know the circumference of the whole circle is C = 2πr.
we know the number of sectors is 360/n.
if we split the whole circle's circumference by the amount of sectors, we end up with a division of the circumference by the sectors
[tex]\bf \cfrac{\stackrel{\textit{whole circle's circumference}}{2\pi r}}{\stackrel{\textit{amount of equally sized sectors}}{\cfrac{360^o}{n^o}}}\implies \qquad 2\pi r\div \cfrac{360}{n}[/tex]
