In this section, we will explore the world of the right angles. By finding answers to what is a sphere, how to calculate it, and discovering interesting right angle facts, the topic will be clear as a crystal.
Before we get started, let’s see what Sam has recently come across.
After observing the angle made by clock hands at 3:00 pm, onefourth piece of a pizza, and the corners of a room, Sam noticed that right angles are all around us at several places. Do you feel the same?
A vertical and horizontal line makes the most common right angles.
Also, diagonal lines intersecting each other form a right angle.
Let's begin our journey and learn the amazing properties of right angles.
Lesson Plan
What Is a Right Angle?
Right angle definition: A right angle is an angle with a value equal to 90 degrees.
It plays an important role in areas of mathematics such as geometry and trigonometry.
When two straight lines intersect each other at 90˚ or are perpendicular to each other at the intersection, they form a right angle. This is all about the right angle definition.
A right angle is represented by the symbol ∟.
The Shape of a Right Angle
A right angle will look like the alphabet L.
Use the interactive simulation given and see how the right angle can be constructed using a protractor or a compass.
Right Angle Examples in Real Life
Examples of right angles in shapes that are available around us are:
 Edges of a door.
 Four edges of television.
 9:30 of the clock.
 Corner of the chair.
Get an idea of the right angles in shapes around us from the picture given below:
These shapes are the most commonly used for giving right angle examples.
Can you find a few more examples of right angles in shapes that are available around you?
Right Angle Calculator
Some of the devices used for measuring the right angle are protractor, the set squares, try square, etc. By playing around with the simulation given below, you can see how it's done.
Protractor
The SetSquares
Try Square
Types of Angles
There are six different types of angles, which are as follows:
An acute angle is less than 90°  

The right angle is 90°  
Obtuse angle lies between 90° and 180° 

A straight angle is 180°  
Reflex angle lies between 180° and 360°  
The full angle is of 360° or 0° 
There is one more place where the right angle is used and that is a rightangle triangle.
If among three angles of a triangle, one angle is 90°, then that triangle is called the right angle triangle.
Since the three interior angles of a right angle triangle add up to 180 degrees, and if one angle is always 90 degrees, then the other two angles must always add up to 90 degrees, and they are called complementary angles.
Right angle triangle
 Protractor, the set squares, and try square are used to measure the right angle in the rightangle triangle.
 There are six types of angles i.e., acute angle, right angle, obtuse angle, straight angle, reflex angle, and full angle.
 Edges of a door, four edges of television, 9:30 of the clock, and corner of the chair are the most common right angle examples.
Solved Examples
Example 1 
Tim had a few angles drawn on a paper. Without using a protractor, can you help him identify the right angle?
Solution
From the right angle definition, a right angle looks like the alphabet L.
Among the given options, the angle in the lower left is a right angle
\(\therefore\) The angle in the lower left which looks like an alphabet Lshaped angle is 90 
Example 2 
Trevor wants to know which types of angles are greater than the right angle. Can you help him figure out this problem?
Solution
From the right angle definition, any angle whose measure is greater than 90° is greater than a right angle.
They are:
(a) Obtuse angle
(b) Straight angle
(c) Reflex angle
(d) Whole angle
\(\therefore\) Obtuse angle, Straight angle, Reflex angle, and Whole angle are greater than 90° 
Example 3 
Hey, can you write the name of the angle shown in the picture, is this an acute angle, obtuse angle, straight angle, reflex angle, or whole angle?
Solution
The name of the angle in the picture is the right angle.
Example 4 
Little Fiona saw the clock in her home and she was curious to know the angle made by two hands of a clock at 9:00 am and 3:00 pm. Do you know the answer to her question?
Solution
we can see in the picture that the two hands of the clock are forming a right angle.
\(\therefore\) The angle made by two hands of a clock at 9:00 am and 3:00 pm isRight angle. 
 Name the possible angle made by the hands of a clock at 12:00 pm and 10:00 am.
 The maximum angle of a reflex angle is?
Interactive Questions
Here are a few activities for you to practice.
Select/Type your answer and click the "Check Answer" button to see the result.
Let's Summarize
We hope you enjoyed learning about the right triangle with the simulations and practice questions. Now, you will be able to easily solve problems on the acute angle, the obtuse angle, type of angles, straight angle, right angle definition, the right angle triangle, the right angle calculator, right angles in shapes, right angle examples, and less than a right angle.
About Cuemath
At Cuemath, our team of math experts is dedicated to making learning fun for our favorite readers, the students!
Through an interactive and engaging learningteachinglearning approach, the teachers explore all angles of a topic.
Be it worksheets, online classes, doubt sessions, or any other form of relation, it’s the logical thinking and smart learning approach that we, at Cuemath, believe in.
Frequently Asked Questions (FAQs)
1. What are the three angles of the right triangle?
The three angles of the right triangle are:
Two acute angles and one right angle.
2. Write the types of angles?
Here are the different types of angles:
Acute angle, aight angle, obtuse angle, straight angle, reflex angle, and full rotation or zero degrees angle.
3. What is an obtuse angle, acute angle, and straight angle?
An obtuse angle is an angle that lies between 90° and 180°
An acute angle is an angle that lies between 0° to 90°
And a straight angle is an angle of 180°
4. What is the right angle, reflex angle, and full rotation angle?
A rightangle is an angle of 90°
A reflex angle is an angle that lies between 180° to 270°
And the full rotation angle is 360° or 0°