90 Degree Angle – Measurement, Definition With Examples

Welcome to another insightful post from Brighterly, the leading platform for fun and engaging educational resources for children. Today, we delve into the fascinating world of geometry to explore one of its most fundamental elements, the 90-degree angle. This concept forms the bedrock for understanding shapes, structures, and spatial relationships. At Brighterly, we believe in making learning an exciting journey, filled with real-life examples and hands-on activities. And that’s precisely what we will do as we unpack the measurement, definition, and examples of the 90-degree angle, or as it is more commonly known, the right angle.

From the corners of a book to the intersections of streets, 90-degree angles are ubiquitous, underlying the design of everyday objects and the natural world. This guide is designed to illuminate these instances, bringing the magical world of angles and geometry to life for young learners.

What is a 90 Degree Angle?

A 90-degree angle is one of the fundamental concepts in geometry, which you can understand better with visual learning. It’s an angle that measures exactly 90 degrees. If you imagine a straight line, and then another line that extends perpendicular from the first, you’ve just created a 90-degree angle. Essentially, it’s the “corner” that is formed when two lines intersect at a right angle. It’s also referred to as a right angle, due to this characteristic right-angled formation.

Definition of a 90 Degree Angle

When two lines intersect and create a square or rectangle’s corner, it’s called a 90-degree angle or a right angle. In simpler terms, when two straight lines meet each other at a point and form a perfect “L” shape, that’s a 90-degree angle. The angle is usually denoted by the symbol “∟”. A practical way to identify a 90-degree angle is that it’s the exact angle formed when you open a book or when the hands of a clock show 3 o’clock.

Properties of a 90 Degree Angle

Several key properties distinguish 90-degree angles. Firstly, it’s half the size of a straight angle, which measures 180 degrees. Secondly, if two angles combine to form a 90-degree angle, they’re called complementary angles. Thirdly, in a triangle, if one of the angles measures 90 degrees, it’s called a right-angled triangle. Lastly, a circle is divided into four equal 90-degree angles at the center. These fascinating properties help us understand and use these angles in our everyday life, whether for building, creating art, or designing objects.

Measurement of a 90 Degree Angle

In terms of measuring a 90-degree angle, it’s best to use an instrument like a protractor. This tool lets you measure angles accurately in degrees. When the protractor’s baseline aligns with one of the lines forming the angle, and the other line meets the 90-degree mark on the protractor, it confirms that you have a 90-degree angle. Math teachers typically introduce this technique early on in the curriculum to build a strong geometric foundation.

90 Degree Angle in Geometry

A 90-degree angle holds a pivotal role in geometry. It forms the corner of squares and rectangles, it’s at the heart of the Pythagorean theorem, and it defines the vertical and horizontal axes on a graph. Without right angles, we would not have the orthogonal coordinate systems which are so fundamental to both pure and applied mathematics, like physics and engineering.

Difference Between 90 Degree Angle and Other Angles

There are several types of angles, and each has different measurements. An angle less than 90 degrees is an acute angle, while an angle greater than 90 degrees but less than 180 degrees is an obtuse angle. A 180-degree angle is called a straight angle, while a 360-degree angle is known as a full rotation or full angle. So, a 90-degree angle stands distinctly as a right angle, marking exactly a quarter of a full rotation.

Examples of 90 Degree Angle in Everyday Life

We encounter 90-degree angles in our everyday life, often without even noticing. Building corners, book edges, squares on a chessboard, street intersections – all exhibit 90-degree angles. Even digital devices like your computer monitor or TV screen typically have 90-degree angles at their corners. Recognizing these can help children understand and appreciatethe practical applications of geometry in daily life.

Creating a 90 Degree Angle – Step-by-step Procedure

Creating a 90-degree angle can be simple. Here is a step-by-step procedure:

  1. Draw a straight line on a piece of paper.
  2. Place a dot on the line where you want your angle to be.
  3. Now, using a ruler, draw another straight line that intersects the first line at the dot.
  4. Adjust this second line until it’s perpendicular to the first line. You’ve now created a 90-degree angle!

Understanding the process of creating these angles will come in handy in various activities, like drafting, crafting, or even advanced geometry problems.

Drawing a 90 Degree Angle using a Protractor

To accurately draw a 90-degree angle, you will need a protractor. Here’s how you can do it:

  1. Draw a straight line and place a point where you want the vertex of your angle.
  2. Place the center of the protractor at the vertex point, aligning the protractor’s baseline with the straight line.
  3. Look for the 90-degree mark on the protractor and draw a line from the vertex point to this mark. Voila, you’ve drawn a perfect right angle!

Using a protractor provides a more precise way of drawing a 90-degree angle and it’s a vital skill in geometric measurements.

Practice Problems on 90 Degree Angle

To further understand the 90-degree angle, here are some practice problems:

  1. Can you draw a 90-degree angle using a protractor?
  2. Can you identify objects in your home that have a 90-degree angle?
  3. If an angle is double the size of a right angle, what is its measure in degrees?

These practice problems can reinforce understanding and promote hands-on learning.


In the vibrant world of geometry, understanding the 90-degree angle provides a vital foundation. By exploring its properties, real-life applications, and the difference it holds with other angles, we unlock a deeper appreciation for the beautiful geometric patterns that construct our world. Through this guide by Brighterly, we’ve not only defined a right angle, but we’ve also helped you recognize its widespread presence, creating a bridge between theoretical learning and practical applications.

At Brighterly, we continually strive to foster an environment that promotes learning through inquiry, exploration, and hands-on activities. This journey through the world of right angles underscores that commitment. Whether you’re constructing a piece of art, solving a complex problem, or simply noticing the design of your surroundings, we hope this understanding of 90-degree angles proves both enlightening and useful.

Frequently Asked Questions on 90 Degree Angle

What is a 90-degree angle?

A 90-degree angle, also known as a right angle, is an angle formed when two straight lines intersect perpendicularly to each other, creating an “L” shape. It measures exactly 90 degrees. The term “right” indicates the conventional rectangular (or “right-angled”) system of coordinates, which forms the basis for Euclidean geometry. This concept is integral to many practical applications, from architecture and design to art and digital graphics.

How to draw a 90-degree angle?

Drawing a 90-degree angle requires precision and the use of a measuring instrument called a protractor. Start by drawing a straight line on a piece of paper, then place a dot at the point where you want the angle to be. Align the center of the protractor with the dot and the baseline of the protractor with the straight line. Locate the 90-degree mark on the protractor and draw a line from the dot to this mark. You’ve successfully drawn a 90-degree angle. Remember, practice is key in mastering this skill.

Where do we see 90-degree angles in everyday life?

The 90-degree angles are omnipresent in our daily lives. Examples abound in both man-made structures and natural forms. Look at the corner of a book or the edges of a table, the intersecting lines on a sheet of graph paper, or the crossroads of a city street – you’re seeing 90-degree angles. Recognizing these examples helps children understand the practical applications of geometric concepts, bridging the gap between textbook learning and the real world.

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