Geometry Notes

Section 1-4 9/11/07

What you’ll learn

 How to measure and classify angles.

 How to identify and use congruent angles and the bisector of an angle.

Vocabulary Terms:

 Degree  Ray  Opposite rays  Angles  Sides of an angle  Vertex of an angle  Interior and exterior of an angle  Right angle, obtuse angle, acute angle  Angle bisector

Ray —a part of a line 

Draw

it with a dot (the endpt) at one end and an arrow at the other 

Name

it with the endpt and one other pt on the ray  

Fact:

2 opposite rays meet at their endpts and make a straight line

Words/Symbols:

 PQ

P Q

Two noncollinear rays intersecting at their endpts make an. . .

Angle

Angle —formed by two noncollinear rays that share a common endpt 

Draw

it with arrows

A



Name

it by  3 noncollinear pts on the angle ( vertex in middle )  The vertex

R

  a number

Words/Symbols:

  ART   R   1

1 T



Facts:

 the 2 rays are the sides  the common endpt is the vertex  angles are measured in degrees

Everyone knows

 Right angles measure 90 º  Acute angles measure between 0 º and 90º  Obtuse angles 180 º measure between 90 º and

Congruent Angles

 Remember congruent means same shape and size  All angles have basically the same shape (two noncollinear rays connected at a common endpoint)  To be congruent two angles must have the same measure.

 Congruent angles will have identical marks

Congruent Angles have identical marks. . .  1   2

1 2

Angle Bisectors-- rays that cut an angle into two smaller congruent angles

A



Draw it T B C

BT bisects  ABC so  ABT   TBC

Have you learned?

 How to measure and classify angles.

 How to identify and use congruent angles and the bisector of an angle.

 P. 34(13-47odd, 51-65odd)