We find the total length of all edges and diagonals of a regular n-sided polygon, inscribed in a unit circle. This involves a very nice use of complex numbers.

00:00 Intro
00:19 Edge lengths
03:13 Diagonal lengths
06:08 Diameter
07:25 Reflex angles
09:13 Sum of lengths
11:52 Using complex numbers
16:23 Making the denominator real
20:09 Taking the imaginary part