A unit circle is simply a circle of radius 1.
1 what?
1 anything.
The most important thing is that if we choose a radius of “1,” it makes it easy to understand the circumference of the circle.
The circumference of a circle is given by C = 2πr.
So the circumference of a unit circle is 2π since 2 * π * 1 = 2π.
This allows us to measure the angle of the circle not in degrees, but in radians, which is a much more useful unit of measure since it is a natural unit.