triangle

Two triangles are similiar, if

1. Their corresponding angles are equal and

2. Their corresponding sides are in the same ratio (or proportion).

A famous Greek mathematician Thales gave an important truth relating to two equiangular triangles which is as follows:

1. The ratio of any two corresponding sides in two equiangular triangles is always the same.

2. It is believed that he had used a result called the Basic Proportionality Theorem (now known as the Thales Theorem) for the same.