If CB and DE are parallel, the ratio of CD to DA and the ratio of BE to EA are equal. In other words, CD/DA = BE/EA . This is often a useful way of solving triangle problems and can be derived from the properties of similar triangles.

GCSE Maths Revision

If CB and DE are parallel, the ratio of CD to DA and the ratio of BE to EA are equal. In other words, CD/DA = BE/EA . This is often a useful way of solving triangle problems and can be derived from the properties of similar triangles.