17.1.2 The Ratio of Two Segments
Core ideaUse one segment as a ruler to measure another, and the number of times it fits is the ratio of the two, AB:CD.
Module goal. Picking up the parallel lines and congruence from quadrilaterals, we carry the idea of a 'ratio' between numbers over to the lengths of line segments, building the language of proportional segments that lays the foundation for everything about similarity to come.