Degree (geometry)

A degree (in mathematics) is 1/360 part of the circle. Imagine the round pie. Cut it through the middle in two parts. Now cut the halves in two equal parts. You now have 4 parts with the right angle where the middle of the pie was. If you cut each of ase in 90 equal slices the will all have an angle of one degree.

Why 90 and not 100?

90 is easier to make calculations with in your head. You can split 90 in equal pieces in many different ways.

2x45, 3x30, 5x18, 6x15, 10x9, 9x10, 15x6, 18x5, 30x3, 45x2 - 10 ways

try this with 100:

2x50, 4x25, 5x20, 10x10, 20x5, 25x4, 50x2 - only 7 ways.

In times when people made calculations in air head the lot ay liked the numbers 360, 90, and 12 better than 10 and 100 for this reason. That is also why are are 12 hours in the day (and 12 in the night), and why the troy pound is 12 ounces.