1. 1 4.2 Congruence and Triangles This presentation was created following the Fair Use Guidelines for Educational Multimedia. Certain materials are included under the Fair Use exemption of the U. S. Copyright Law. Further use of these materials and this presentation is restricted.

2. 2 Objectives Students will identify congruent figures and corresponding parts. Students will prove that two triangles are congruent.

3. 3 Theorem 4.3: Third Angles Theorem If two angles in one triangle are congruent to two angles in another triangle, then the third angles are congruent. http://www.themathlab.com/geometry/mathcourt/level7/reasonslevel7.htm

4. 4 Vocabulary congruent – when two figures are congruent, there is correspondence between the sides and angles such that corresponding angles are congruent and corresponding sides are congruent.

5. 5 Example 1 58° E F G H J StatementsReasons 1.Corresponding sides are  2.  EFG   JHG 3.  FGE   HGJ 4.  HJG   FEG 5.  EFG   JHG 1.Given 2.Given 3.vert.  s 4.3 rd  s Th. 5.Def. of   s Given: See diagram Prove:  EFG  JHG

6. 6 Example 2 120° 20° StatementsReasons 1.Corr. Sides are  2.  ECD  PQD,  CED  QPD 3.  EDC   PDQ 4.  CED  QPD 1.Given 2.Given 3.3 rd  s Th. 4.Def. of   s Given: see diagram Prove:  CED   QPD C E D P Q