We will next consider adjacent angles, supplementary angles, complementary
angles, vertically opposite angles and angles forming a circle.
Adjacent Angles
Angles that lie on either side of a common arm are said to be **adjacent**.
Remember:
The **sum of adjacent angles forming a straight line** is 180º.
Two such angles are also known as **supplementary adjacent angles**.
Supplementary angles are introduced below.
Example 3
Use the information given in the diagram to find *x*.
##### Solution:
So, the value of *x* is 136º.
Example 4
Use the information given in the diagram to find *x*.
##### Solution:
So, the value of *x *is 18°.
Supplementary Angles
If the sum of two angles adds up to 180°, then the angles are said to be **supplementary**.
The supplement of 40º is 140º.
The supplement of 140º is 40º.
Complementary Angles
If the sum of two angles adds up to 90°, then the angles are said to be **complementary**.
The complement of 55° is 35°.
The complement of 35° is 55°.
Example 5
What is the complement of 38°?
##### Solution:
Method for Finding the Value of a Pronumeral
To find the value of the pronumeral from the given information, write an equation. Then solve the equation and write the answer in words.
#### Example 6
What is the supplement of 38°?
##### Solution:
Key Terms
adjacent angles, supplementary
adjacent angles, supplementary angles, complementary
angles |