Math Planet
Math Planet: Geometry: Measure Line Segments
Explores how to measure the length of a line segment through examples and a video lesson. [0:40]
Mathigon
Mathigon: Geometry: Circle and Pi: Degrees and Radians
Rather than dividing a circle into some number of segments (like 360 degrees), mathematicians often prefer to measure angles using the circumference of a unit circle - a circle with radius 1. This way of measuring angles is called...