1. Angle- Formed by two rays, the common endpoint is called the vertex.
2. Ray- take a point on a line and all the points on the line that lie to one side of that point
indicate a ray. For example, take a point L on a line and all the points on the line that lie
to one side of L give us a ray LM.
3. Straight Angle- The figure form by two opposite rays, straight angle = 180
4. Interior of an Angle- The region of the plane sandwiched between the two sides of the
5. Exterior of an Angle- The remainder of the plane that is not inside the sides of the
6. Measure of an Angle- use a protractor and place the center of the protractor over the
vertex of the angle.
7. Angle Addition Postulate- If R is in the interior of PQS, then mPQR + mRQS =
mPQS. If mPQR + mRQS = mPQS, then R is in the interior of PQS.
8. Naming an Angle- To name an angle you name a point on one ray, the vertex, and then
a point on the second ray. The vertex must be the center point when you name the angle.
You may also use just the vertex to name the angle.
9. Acute Angle- an angle less than 90
10. Obtuse Angle- An angle grater than 90
11. Right Angle- an angle that equals exactly 90
12. Congruent Angles- two angles that have the same angle measures
13. Angle Bisector- a ray whose endpoint is the vertex of a larger angle and divides the
larger angle into two congruent angles.