Warm-up The roundest knight at King Arthur’s round table was Sir Cumference He acquired his size from too much pi. When the butcher backed into the meat grinder… He got a little behind in his work.

Agenda Homework Review Chapter 4 Identifying Congruent Triangles 4-2 Measuring Angles in Triangles 4-1, 4-2 Enrichment

4-1 Study Guide

4-1 Practice

4-1 Classifying Triangles Review

4-2 Measuring Angles in Triangles Theorem 4-1 Angle Sum Theorem The sum of the measures of the angles of a triangle is 180.  A +  B +  C = 180 A line or “straight angle” is exactly 180 degrees.

4-2 Measuring Angles in Triangles Theorem 4-2 Third Angle Theorem The basis of this proof is that if both triangles total 180 degrees, and both triangles have two identical angles... then the third angle would be the same remainder. Third angle congruence shows up throughout many units.. remember it.

4-2 Measuring Angles in Triangles Theorem 4-3 Exterior Angle Theorem The measure of an exterior angle of a triangle is equal to the sum of the measures of the two remote interior angles. In the figure to the left,  BCD is an exterior angle of triangle ABC. An EXTERIOR ANGLE is formed by one side of a triangle and the extension of another side. The interior angles of the triangle not adjacent to a given exterior angle are called REMOTE INTERIOR ANGLE. Thus in the above case,  A and  B are the remote angles to the exterior angle  BCD.

4-2 Measuring Angles in Triangles Corollary The acute angles of a right triangle are complementary. Corollary There can be at most one right or obtuse angle in a triangle. By the way.... what is a corollary? A COROLLARY is a statement that can be easily proved using a theorem..... A better way of saying this... is that a corollary is a fact or statement that directly falls from a given theorem.

4-2 Measuring Angles in Triangles 137  105  75  61  37  143  37  68  98 

Answers Ahead

4-2 Study Guide

Homework 4-2 Study Guide and Practice 4-1, 4-2 Enrichment