1. Angles

2. A) Terms
1) Angle – consists of 2 different rays that have the same endpoint.
a) rays are called the sides
b) the endpoint is called the vertex
c) angles are measured in degrees using a protractor.
d) symbol for angle: “<“
e) measure <B denote: m<B or
measure <ABC denote: m<ABC
f) congruent angles are angles that have the same measure.
denote: <ABC <DEF

3. C) Other Terms:
1) A point is in the interior of an angle it it is between the 2 rays or inside the angle.
2) A point is in the exterior of an angle if it lies outside the angle.
Ex.
exterior
interior

4. 3) Classify Angles:
a) Acute Angle - measures less than 90°.
b) Right Angle – measures 90°
c) Obtuse Angle – measures between 90° and 180°.
d) Straight Angle – measures 180°
Ex. Label the Angles below.
1) ) ) 4)

5. 4) Two angles are Adjacent angles if they share a common vertex and side, but have no common interior points.
Ex.
A C
B D
<ABC is adjacent to <CBD

7. 5) Angle Bisector
- is a ray that divides the angle in half
Ex. Find x. BC bisects <ABD. <ABC = x + 3 and <CBD = 3x – 1.

8. B) Postulates 1) Postulate 3: Protractor Postulate
- The measure of angles are from 0° to 180°.

9. 2) Postulate 4: Angle Addition Postulate
If P is in the interior of <RST, then m<RSP + m<PST = m<RST
Ex R m<RSP
P m<RST
S m<PST T