**1.3: Measuring and Constructing Angles**

Definitions:

Angle- A figure formed by two rays, or sides, with a common endpoint called a vertex.

Definitions:

Angle

**Interior of an**

**Angle**- The set of all points

__between__the sides of the angle.

**Exterior of an**

**Angle**- The set of points

__outside__of the angle.

- Measure of an angle is interior of an angle, measured in

**degrees.**

- One degree is 1/360 of a circle.

- Angles can be measured with

**protractors.**

**Acute**

**Angle**- An angle thatmeasures greater than 0º and

__less than 90º.__

**Right Angle**- An angle that measures

__90º.__

**Obtuse Angle**- An angle that measures

__greater than 90º and less than 180º.__

**Straight**

**Angle**- An angle formed by two opposite rays and

__measures 180º.__

**Congruent**

**Angles**- Angles that have the same measure.

**Angle Bisector**- A ray that

__divides__an angle into

__two congruent__angles.

**Postulates:**

Postulate 1-3-2- If S is the interior of angle PQR then the measure of angles PQS and SQR= the measure of angle PQR.

Postulate 1-3-2

**Examples:**