Supplementary Angles, Definition & Examples

Supplementary Angles, Properties, Examples and Solution

Angles are Supplementary Angle if Sum Of Two Angles 180 degrees. These two angles (135° and 45°) are Supplementary Angle, because sum of 135°+45°=180°.

  • Supplementary Angles together make a straight line, But the angles don't have to be together.
  • When the two angles sum 180°, they "Supplement" each other.
  • When two adjacent angles form a straight line, they are supplementary.
  • If one angle is known, its supplementary angle can be found by subtracting the measure of its angle from 180°. 

Fig 1 Example of Supplementary Angles, because sum of angle a and b are 180°. 


Fig 1: Supplementary Angles
Determine supplement Angle
To determine the Supplement, subtract the given angle from 180.
Example 1: If one angle is 50 degree, find the second angle if the two angles are supplementary to each other.
Solution: 180 - 50 = 130°,  The Supplement of 50° is 130°.
Example 2: If one angle is 60 degree, find the second angle if the two angles are supplementary to each other.
Solution: 180 - 60 = 120° ,  The Supplement of 60° is 120°.
Example 3: If one angle is 30 degree, find the second angle if the two angles are v to each other.
Solution: 180 - 30 = 150°,  The Supplement of 30° is 150°.
Example 4: If one angle is 15 degree, find the second angle if the two angles are supplementary to each other.
Solution: 180 - 15 = 165° ,  The Supplement of 15° is 165°.
Some other examples of supplementary angle pairs
20 degrees and 160 degrees
40 degrees and 140 degrees
60 degrees and 120 degrees
70 degrees and 110 degrees
90 degrees and 90 degrees

Practice Problems
Example 1: The measure of angle 1 is 27 degree and angle 2 is 150 degree. Identify whether the angles are supplementary to each other or not?

Example 2: Let first angle is 12 degrees, find the second angle if the two angles are supplementary to each other?

Example 3: x and y are supplementary angles. Given x = 45˚, find the value y?

Example 4: The measure of angle 1 is 27 degree and angle 2 is 150 degree. Identify whether the angles are supplementary to each other or not?

Example 5: Let first angle is 22 degrees, find the second angle if the two angles are supplementary to each other?

Example 6: The measure of angle 1 is 10 degree and angle 2 is 120 degree. Identify whether the angles are supplementary to each other or not?

Example 7: Let first angle is 120 degrees, find the second angle if the two angles are supplementary to each other?

Example 8: The measure of angle 1 is 15 degree and angle 2 is 145 degree. Identify whether the angles are supplementary to each other or not?

Example 9: Let first angle is 12 degrees, find the second angle if the two angles are supplementary to each other?

Example 10: The measure of angle 1 is 30 degree and angle 2 is 135 degree. Identify whether the angles are supplementary to each other or not?


Practice Problems for Home Work 
Example 1 : The measure of angle 1 is 27 degree and angle 2 is 150 degree. Identify whether the angles are supplementary to each other or not?

Example 2 : Let first angle is 12 degrees, find the second angle if the two angles are supplementary to each other?

Example 3 : x and y are supplementary angles. Given x = 45˚, find the value y

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