Triangles – Notes

Similarity of Triangles

Two triangles are similar, if their corresponding angles are equal and their corresponding sides are proportional or in the same ratio.

Basic proportionality Theorems: If a line is drawn parallel to one side of triangle to intersect the other two sides in distinct points, the other two sides are divided in the same ratio.

Converse of the Proportionality Theorem: if a line divides any two sides of a triangle in the same ratio, then the line is parallel to the third side.

Lines parallel to the same line are parallel to each other. 

Criteria for Similarity of Triangles

Two triangles are similar, if their corresponding angles are equal and their corresponding sides are in same ratio (or proportion).