1.  What is an angle?  Two different rays with the same endpoint.  Rays are the sides, endpoint is the vertex.  Named with 3 points or by the vertex. vertex sides

2.  Example  Name the angles you see in the diagram A C D E

3.  Measuring angles with a protractor  Different types of angles:  Write either <ABC is 32º or m<ABC=32º  Acute (less than 90º)  Obtuse (more than 90º  Right angle (exactly 90º)  Straight (180º)

4.  Example  Postulate 4: Angle Addition  Page 25 in textbook  If P is in the interior of <RST, then the measure of <RST is equal to the sum of the measures of <RSP and <PST

5.  Example  Given the m<GFJ=155º, find m<GFH and m<HFJ

6.  Example  Given that <VRS is a right angle, find m<VRT and m<TRS

7.  Congruent angles  2 angles are congruent if they have the same measure (curved line)  <A <B A B

8.  Example  Identify all pairs of congruent angles  If m<P=120º, what is m<N?

9.  Angle Bisector  A ray that divides an angle into 2 angles that are congruent.  WY bisects <XWZ

10. Examples