Supplementary Angles
Concept
Two angles are said to be supplementary angles if they add up to 180 degrees. Supplementary angles form a straight angle (180 degrees) when they are put together. In other words, angle 1 and angle 2 are supplementary, if Angle 1 + Angle 2 = 180 degrees.
Rules
Supplementary angles are two angles whose sum is 180 degrees. To find the missing angle, subtract the given angle from 180 degrees.
Example
Find the measure of x in the figure.
Solution
The angles are supplementary. Supplementary angles are two angles whose sum is 180 degrees.
x + 107° = 180°
x + 107° – 107° = 180° – 107°
x = 73°
Practice Supplementary Angles
Practice Problem 1
Identify each pair of angles as vertical, supplementary, or complementary angles.
Practice Problem 2
Find the measure of x in the figure.
Practice Problem 3
The measure of angle A is 111°, find the measure of its supplementary angle.
Practice Problem 4
Find the measure of the obtuse angle using data from the picture.
An angle is a figure formed by two rays, called the sides of the angle, sharing a common endpoint, called the vertex of the angle.
Vertex – is the point where two rays of an angle meet.
Adjacent Angles – Two angles are adjacent if they share a common vertex, a common side, and do not overlap.
Vertical angles are a pair of opposite angles formed by intersecting lines. Vertical angles are always congruent.
Supplementary angles are two angles whose sum is 180 degrees
Complementary angles are two angles whose sum is 90 degrees.
Congruent Angles – Two angles are said to be congruent if their corresponding sides and angles are of equal measure.
Pre-requisite Skills
Measuring Angles
Classifying Angles
Drawing Angles
Estimating Angles
Angles
