Look at the sector of the circle shown below. To calculate the length of the arc, we need to know what fraction of the circle is shown. To do this, we use the angle and compare it with 360˚.

GCSE Edexcel Circles, sectors and arcs - Edexcel Arc length The circumference of a circle is its outside edge, and is the same distance from the centre at every point along its length.

Blackburn's formula does this by sketching the arc of your car's turning capability into a full circle, then using the center of the circle to create the right-angle triangles Pythagoras loved ...

An alternate idea, using integral calculus is to define π as the arc length of the upper half of the circle x² + y² = 1, the formula for which is ...