Not to be confused with angels, angles are the pointed corners of shapes. Angles can be named three different ways.
This angle could be named any of these ways:
(counterclockwise)
(clockwise)
(just the vertex)
Look Out: when naming an angle using three letters, the vertex must always be the middle letter!
Types of Angles
| Name | Description | Example |
| Acute Angle | An angle less that 90°.
Lame joke: this angle is so small and a-cute! |  |
| Obtuse Angle | An angle greater than 90°, but less than 180°. |  |
| Right Angle | An angle that is exactly 90°.
This is commonly denoted with a small box in the corner. |  |
| Straight Angle | A 180° angle. It's - you guessed it - a straight line. |  |
| Supplementary Angles and Linear Pairs | Angles that add up to 180°. are supplementary angles.If the two angles are adjacent (next to each other) and add up to 180°, they are a linear pair. are also a linear pair. |  |
| Complementary Angles | Angles that add up to 90°.
 are complementary.
|  |
| Vertical Angles | When two lines intersect, opposite angles are called "vertical angles". Vertical angles are congruent.   |  |
See the squiggly line over the equal sign above? This symbol means congruent. Oh, and btw, congruent angles have the same measurement.
Example 1
Are the following angles complementary or supplementary?
|
and 
are supplementary angles, even though they aren't next to each other, because they add up to 180°. Example 2
Are the following angles complementary of supplementary?
|
and 
are complementary because, even though they are not adjacent, they add up to 90°. Example 3
Name the following angles and angle pairs in the image below:
|
and 
are also vertical angles, so they are congruent. Since ∠VXY & ∠YXU are both right angles, they're congruent as well. 
