1. U1.2 Angles and Lines at a Point
(textbook 1.5)

2. An angle is formed when two rays share a common vertex.
Parts of an angle
ray BC
vertex
An angle is formed when two rays share a common vertex. C B A
ray BA

3. Types of Angles RIGHT = 90◦ ACUTE < 90° OBTUSE > 90° and
< 180°
STRAIGHT
= 180°

4. Angle Pairs Complementary Angles : angles whose sum is 90°
Supplementary Angles :
angles whose sum is 180°

5. Share a vertex and a side
Angle Pairs
70°
60°
110°
60°
Vertical Angles :
Opposite and equal
Adjacent Angles :
Share a vertex and a side

6. Angle Pairs Linear Pair: Adjacent and Supplementary
60°
60°
100°
30°
80°
30°
100°
80°
100°
80°
Linear Pair:
Adjacent and Supplementary
Adjacent angles on a “line” add to 180°
Angles at a “point” add to 360°

7. Naming Angles
< A
<BAC
<CAB
<1 C A 1 B

8. Naming Angles <a, <b, & <c <1, <2, & <3O
<a, <b, & <c
<1, <2, & <3
<NML & <LMN
<LMO & <OML
<NMO & <OMN

9. Angle Addition Postulate
If a point S lies on the interior of <PQR, then <PQS + <SQR = <PQR +
15° =
65°
50° P
50° Q
15° S R