Supplementary Angles – Definition With Examples
10 minutes read
Created: January 14, 2024
Last updated: January 14, 2024
Welcome to another fascinating exploration of the universe of mathematics with Brighterly, your reliable partner in making learning not just easy, but also fun and engaging! Today, we’re shedding light on a fundamental yet exciting concept – Supplementary Angles. Whether we’re looking at a halfeaten pizza or the hands on a clock, Supplementary Angles pop up in numerous places in our everyday lives, often without us even noticing! These angles are the indispensable blocks of the geometric world, forming a straight line and paving the way for more complex and intriguing shapes. As we embark on this mathematical adventure, remember that at Brighterly, we aim to make the journey just as thrilling as the destination. So let’s get started!
Supplementary Angles
Imagine two angles standing side by side, their arms reaching out to form a straight line. These angles are special. They’re called Supplementary Angles, and they add up to 180 degrees. Just like building blocks that complete a castle, these angles complete each other to form a perfect halfcircle or straight angle. Understanding these angles helps us with everything from simple geometry problems to realworld construction designs. Let’s dive into the intriguing world of Supplementary Angles!
What Are Supplementary Angles?
Now, you might be wondering, what exactly are Supplementary Angles? Let’s break it down. First, we need to understand the basic building block of this concept – the Angle.
Definition of an Angle
An angle is formed when two lines or rays meet at a common point, known as the vertex. The amount of rotation about the vertex that one line must undertake to coincide with the other line is the measure of the angle, expressed in degrees. The concept of angles is a fundamental part of mathematics and can be seen in various branches such as geometry and trigonometry.
Definition of Supplementary Angles
Now that we understand angles, let’s define Supplementary Angles. These are two angles whose measures, when added together, total 180 degrees. If the measures of two angles add up to 180 degrees, those angles are supplementary. Picture a straight line divided into two parts by another line. Each of these parts forms an angle with the dividing line, and these angles are supplementary!
Properties of Angles
Let’s dive a bit deeper into angles. Angles have various properties that make them unique and distinguishable. The first is their measure, which can range from 0 degrees to 360 degrees. The second property of an angle is its name, usually derived from its measure. For example, an angle measuring 90 degrees is called a right angle, while an angle measuring less than 90 degrees is an acute angle.
Properties of Supplementary Angles
Supplementary Angles have some interesting properties. The primary property is their measure – the sum of the measures of supplementary angles always equals 180 degrees. Also, if two angles are supplementary to the same angle, then those angles are congruent, meaning they have the same measure. Lastly, if a line is perpendicular to one of two supplementary angles, it is also perpendicular to the other.
Difference Between Supplementary and NonSupplementary Angles
The key difference between Supplementary and NonSupplementary Angles is their sum. Supplementary Angles always add up to 180 degrees, forming a straight line. NonSupplementary Angles, on the other hand, don’t have this property. Their measures can add up to less than, equal to, or more than 180 degrees, but they don’t necessarily form a straight line.
Equations of Supplementary Angles
One exciting aspect of Supplementary Angles is that they can be represented using equations. If you know the measure of one angle, you can always find the measure of its supplementary angle by subtracting it from 180 degrees. So if the measure of one angle is ‘x’ degrees, the measure of its supplementary angle is ‘180 – x’ degrees.
Writing Equations for Supplementary Angles
Now, let’s understand how to write equations for Supplementary Angles. If you have two angles, ‘a’ and ‘b’, and they are supplementary, you can write the equation as ‘a + b = 180’. This equation represents the fact that the sum of the measures of the two angles is 180 degrees.
Practice Problems on Supplementary Angles
Now that we’ve mastered the theory, let’s put our knowledge to the test with some Practice Problems on Supplementary Angles! Solving these problems will help solidify the concept and get us one step closer to becoming Supplementary Angles wizards!

Problem: If one angle measures 87 degrees, what is the measure of its supplementary angle?
Solution: The supplementary angle can be found by subtracting the given angle from 180 degrees. So, 180 – 87 = 93 degrees. Thus, the supplementary angle is 93 degrees.

Problem: Two angles are supplementary. If one angle measures x degrees, and the other is twice as large, can you write an equation to find the value of x?
Solution: Since the angles are supplementary, they add up to 180 degrees. The equation becomes x + 2x = 180. Simplifying this, we get 3x = 180. Solving for x, we find that x = 60. Thus, the two angles are 60 degrees and 120 degrees respectively.

Problem: One angle is 30 degrees more than twice its supplementary angle. Can you find the measures of both angles?
Solution: Let’s denote the supplementary angle as x. According to the problem, our angle is 2x + 30. Since they’re supplementary, their sum should be 180 degrees. The equation will be x + 2x + 30 = 180. Solving this equation, we find x = 50 degrees. Consequently, our angle is 2*50 + 30 = 130 degrees. So, the two supplementary angles are 50 degrees and 130 degrees.

Problem: If an angle is five times its supplementary angle, what are the measures of both angles?
Solution: Let the supplementary angle be x. The given angle is 5x. Since they’re supplementary, x + 5x = 180. This simplifies to 6x = 180, and solving for x gives x = 30 degrees. Therefore, our angle is 5*30 = 150 degrees. Thus, the two angles are 30 degrees and 150 degrees.
Try these problems at home, and soon, you’ll find that working with supplementary angles becomes second nature!
Conclusion
Our journey through the world of Supplementary Angles has been an enlightening one, hasn’t it? With Brighterly, we’ve navigated through definitions, properties, equations, and practical problems, transforming seemingly abstract ideas into tangible knowledge that we can use both in the classroom and beyond. We’ve witnessed how these angles add up to 180 degrees, forming a straight line, and how this simple concept is integral to our understanding of geometry and space.
While math might seem like a labyrinth at times, remember that with every concept we master, we’re moving one step closer to the center. In this labyrinth of learning, Brighterly is your guiding light, illuminating the path and making learning a joyous journey. So keep exploring, keep questioning, and most importantly, keep enjoying the learning process. After all, as our journey through Supplementary Angles has shown us, every angle counts!
Frequently Asked Questions on Supplementary Angles
Can two acute angles be supplementary?
No, two acute angles (angles less than 90 degrees) cannot be supplementary. The sum of two acute angles would be less than 180 degrees, and hence, they can’t be supplementary.
Can two obtuse angles be supplementary?
No, two obtuse angles (angles more than 90 degrees but less than 180 degrees) cannot be supplementary. The sum of two obtuse angles would be more than 180 degrees, which defies the definition of supplementary angles.
If two angles are supplementary and one is a right angle, what is the measure of the other angle?
A right angle measures 90 degrees. Since supplementary angles add up to 180 degrees, the other angle must also be a right angle, measuring 90 degrees.
Can an angle be supplementary to itself?
Yes, an angle can be supplementary to itself if it measures 90 degrees. Since the sum of the measures of supplementary angles is 180 degrees, an angle that measures 90 degrees would be supplementary to another angle of 90 degrees, which could be itself.
Can an angle have more than one supplementary angle?
Yes, an angle can have more than one supplementary angle. For example, an angle of 60 degrees is supplementary to angles of 120 degrees, irrespective of how the 120degree angle is obtained (e.g., 60 + 60, 90 + 30, 100 + 20, etc.). The key requirement is that the measures of the two angles should add up to 180 degrees.
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