Chapter 11 Preliminaries

The mathematical definition for similar triangles is that they both have correponding angles that are equal.

Recall that the sum of all 3 angles in a triangle total 180^o.

This means that if you know that 2 angles in 2 different triangles are the same, then the 3rd angle must also be the same in both triangles. Therefore, the triangles are similar

For similar triangles, the lengths of the corresponding sides are in proportion.

For example, if the sides of one similar triangle are A, B, and C and the corresponding sides of the other similar triangle are a, b, and c, then

a/A = b/B = c/C

An Example