 CALCULUS Understanding Its Concepts and Methods

Similar triangles

If and are lines, then the ratio of to , written , is the length of divided by the length of .

The sides of are proportional to the sides of if the three ratios , , and are equal.

Two triangles are similar if their angles are equal and their sides are proportional.  • If the angles of a triangle are equal to the angles of another triangle, then the two triangles are similar.

• A line that divides two sides of a triangle proportionally is parallel to the third side.

• If two sides of one triangle are proportional to two sides of another and the included angles are equal, then the triangles are similar.

• If the sides of one triangle are proportional to the sides of another triangle, then the triangles are similar.

Ratio and Proportion

• If or , then and .

• If , then .

Copyright © 2006 Darel Hardy, Fred Richman, Carol Walker, Robert Wisner. All rights reserved. Except upon the express prior permission in writing, from the authors, no part of this work may be reproduced, transcribed, stored electronically, or transmitted in any form by any method.