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An ** angle** is the union of two rays having the same endpoint. The endpoint is called the

Objects of the same shape and size are said to be ** congruent**.

An L-shaped angle is called a ** right angle**. A right angle will always measure

An angle whose sides form a straight line is called a ** straight angle** and has a measure of

An ** acute angle** is an angle whose measure is

An ** obtuse angle** is an angle whose measure is

Many special relationships exist between pairs of angles.

Let's take a look at them . . .

Two angles are ** adjacent** if they have the same vertex and share a common side, but do not overlap or have any points in common.

Two angles are ** complementary** if the sum of their measures is 90°. When this occurs, either angle is called the

When two angles are **adjacent and complementary**, do you know what type of angle is formed by their exterior sides??

Two angles are ** supplementary** if the sum of their measures is 180°. When this occurs, either angle is called the

When two angles are **adjacent and supplementary**, do you know what type of angle is formed by their exterior sides??

When two lines intersect, they always form four angles with a common vertex. Each pair of angles which are not adjacent (and therefore opposite) are called ** vertical angles** and are equal in measure.

How about this for a new angle . . .

Let's try some Practice Problems !

- If two angles are supplementary, find the measure of the smaller angle if the measures of the two angles are in the ratio of: a) 1 : 8 b) 3 : 5
- If two angles are complementary, find the measure of the smaller angle if the measures of the two angles are in the ratio of: a) 2 : 3 b) 3 : 1
- The measure of the supplement of an angle is three times as great as the measure of the complement of the same angle. What is the measure of the angle?
- The difference between the measures of an angle and its complement is 14. Find the measure of the smaller of the two angles.
- The difference between the measures of an angle and its supplement is 22. Find the measure of the smaller of the two angles.

If you've mastered Angles, you'll do great with Triangles!