Let’s talk about circles for a moment. We all know what it looks like we see them everyday on cars, pictures, etc. I believe most of you are familiar with the math term pi, π=3.14. Now let me ask how many of you ever heard of a term called arc length. Arc length is the measurement of a line on a curved surface. To measure distance of the arc length is by radians. Another thing is to measure the ratio of a circle is the arc length by the radius. Also an interesting bit if you increase the radius of the circle the ratio will remain the same .
In the chart above 180° is equal to π, for 45° it will equal to 1π/4, and π/2 will be equivalent to 90°.