CK12 - Geometry

The trianglein the diagramis an isoscelestriangle.To find the congruentangles,you needto find the angles
that are oppositethe congruentsides.

This diagramshowsthe congruentangles.The congruentanglesin the triangleare and
.

So, how do we provethe baseanglestheorem?Usingcongruenttriangles.

Given:Isosceles with

Prove

Statement Reason

1. Given


2. is isosceleswith
   .


3. ConstructAngleBisector 2. AngleBisectorPostulate


4. 
   
   
   
   3. Definitionof AngleBisector
   
   
   
   


5. 
   
   
   
   4. ReflexiveProperty
   
   
   
   


6. 
   
   
   
   5. SAS Postulate