1. Measures and Relationships

2.  Ray – part of a line that includes one endpoint and extends infinitely in one direction  Opposite rays – rays that share a common endpoint and are collinear  Angle – object formed from two noncollinear rays that have a common endpoint.  Sides – the rays that form the angle  Vertex – the common endpoint of an angle

3.  An angle divides a plane into three parts: On the angle, the interior of the angle, the exterior of the angle  Angles are measured in units called degrees; a degree is the result of dividing the distance around a circle into 360 parts.

4.  Acute Angles – measure between 0 and 90 degrees  Right Angles – measure exactly 90 degrees  Obtuse Angles – measure between 90 and 180 degrees

5.  An angle bisector is a ray that divides an angle into two congruent angles.

6.  Adjacent angles – two angles that that lie in the same plane and have a common vertex and a common side, but no common interior points

7.  Linear Pair – a pair of adjacent angles with noncommon sides that are opposite rays

8.  Vertical Angles – two nonadjacent angles formed by two intersecting lines  Vertical not Vertical

9.  Complementary angles – two angles with measures that add to 90 degrees  Supplementary angles – two angles with measures that add to 180 degrees

10.  Intersect to form four right angles  Intersect to form congruent adjacent angles  Segments and rays can be perpendicular to lines or other segments and rays

12.  Are there any aspects of life where angles are important?  What careers paths make extensive use of angles and angle relationships?  In what ways do you use angles?