Angles and circular measure
The degree has been in use since Babylonian times (over 4000 years) and is the unit of angular
measure most people are familiar with.
The SI standard unit of angular measure is the radian (rad). Most
mathematicians use rads because it facilitates many calculations.
Beware the mil! In the SI system of measurement the millirad
is 1/1000th part of a radian. The milliradian is often abreviated mil.
and the unit is used by the military to calculate gun
aiming angles. However to 'simplify' the process some millitary authorities
have decided to vary the number of mils in a radian. Outside the UK the size of a mil
depends on who you are talking to.