# Obtuse Angle – Definition with Examples

Updated on December 31, 2023

Welcome to Brighterly, where we make learning geometry fun and engaging for children! In this article, we will dive deep into the world of obtuse angles. Obtuse angles play a significant role in the fascinating field of geometry, and their unique properties make them an important topic for kids to explore. We aim to provide a comprehensive understanding of obtuse angles in a way that sparks curiosity and encourages young minds to learn more about the amazing world of math.

## What is an Obtuse Angle?

An obtuse angle is a unique type of angle that has fascinating properties and applications. In geometry, angles are classified into three major categories based on their degree measurements: acute angles, obtuse angles, and right angles. Specifically, an obtuse angle is one that measures more than 90 degrees but less than 180 degrees. This means that it’s larger than a right angle, which measures exactly 90 degrees, but smaller than a straight angle, which measures 180 degrees. In this article, we’ll explore the different aspects of obtuse angles, their properties, and how they relate to various geometrical shapes, as well as real-life examples.

## Obtuse Angle Definition

The definition of an obtuse angle is an angle whose measure is greater than 90 degrees but less than 180 degrees. In other words, if you have an angle whose measure is between 90 and 180 degrees, you can confidently say that it’s an obtuse angle. This unique property distinguishes obtuse angles from acute angles, which measure less than 90 degrees, and right angles, which measure exactly 90 degrees.

## Obtuse Angle of a Triangle

A triangle is a three-sided polygon, and its angles are the primary focus of many geometry problems. A triangle can have different types of angles, including acute, right, and obtuse angles. When it comes to obtuse triangles, these have one obtuse angle and two acute angles. Since the sum of a triangle’s interior angles is always equal to 180 degrees, the other two angles in an obtuse triangle must be acute to satisfy this requirement.

## Obtuse Angle of a Rhombus

A rhombus is a special type of parallelogram where all four sides have equal length. It is also known as a diamond shape. The angles of a rhombus can either be acute or obtuse, but not right angles. When discussing the obtuse angle of a rhombus, we’re referring to the angle that measures more than 90 degrees. In a rhombus, the obtuse angles are always opposite to each other, and their measures add up to 180 degrees.

## Obtuse Angle of a Parallelogram

A parallelogram is a quadrilateral with opposite sides parallel. Like a rhombus, the angles of a parallelogram can be acute or obtuse, depending on the shape’s specific properties. When discussing the obtuse angle of a parallelogram, we are referring to the angle that measures more than 90 degrees. The obtuse angles in a parallelogram are opposite to each other, and their measures also add up to 180 degrees.

## Obtuse Angle Degree

The degree of an obtuse angle is a numerical value that represents its measure. As previously mentioned, an obtuse angle is any angle that measures more than 90 degrees but less than 180 degrees. So, an obtuse angle’s degree can range anywhere between 91 and 179 degrees. This wide range of possible values makes obtuse angles quite versatile in geometric problems and real-life applications.

## Obtuse Angles in Real Life

Obtuse angles are not just theoretical constructs; they have many practical applications in the real world. They can be found in everyday objects like scissors, doors, and various architectural designs. For example, the roof of a house may have obtuse angles to allow for better water drainage, or a bridge might be designed with obtuse angles to provide improved structural support. These real-life examples demonstrate the importance of understanding obtuse angles and their properties in various contexts.

## Acute and Obtuse Angles

Both acute and obtuse angles are essential concepts in geometry, and they share certain similarities while also possessing distinct differences. Acute angles measure less than 90 degrees, while obtuse angles measure between 90 and 180 degrees. They can both be found in various geometric shapes, like triangles, rhombi, and parallelograms. Understanding the difference between acute and obtuse angles is crucial for solving geometry problems and recognizing their applications in real-life situations.

## Obtuse Angle Examples

Let’s look at a few examples of obtuse angles to better understand their properties and applications:

- A door slightly ajar creates an obtuse angle between the door and the door frame.
- A pair of scissors, when opened, forms an obtuse angle between the two blades.
- In an obtuse triangle, the largest angle is always an obtuse angle.
- The opposite angles of a parallelogram with obtuse angles are also obtuse and have the same degree measurement.

These examples show the versatility of obtuse angles and their presence in various geometric shapes and everyday objects.

## Practice Questions on Obtuse Angle

To further enhance your understanding of obtuse angles, try answering the following practice questions:

- If an angle measures 110 degrees, is it an obtuse angle? Explain your answer.
- Can a right triangle have an obtuse angle? Why or why not?
- In a parallelogram, if one angle measures 120 degrees, what are the measures of the other three angles?
- Can a rectangle have an obtuse angle? Explain your reasoning.

## Conclusion

In conclusion, obtuse angles are an integral part of geometry, with a wide range of applications in both theoretical and real-life contexts. By understanding the properties of obtuse angles, their relation to other types of angles, and their presence in various geometric shapes, children can master the fundamentals of geometry and develop a strong foundation for future mathematical endeavors. At Brighterly, we believe in nurturing a child’s innate curiosity and passion for learning, and we strive to make complex concepts like obtuse angles accessible, enjoyable, and engaging for young learners. With this knowledge, children will be better equipped to recognize the practical uses of obtuse angles in everyday situations, opening their eyes to the beauty and wonder of the mathematical world around them.

## Frequently Asked Questions on Obtuse Angle

### What is an obtuse angle?

An obtuse angle is a type of angle found in geometry, which measures more than 90 degrees but less than 180 degrees. Obtuse angles are larger than right angles, which measure exactly 90 degrees, and smaller than straight angles, which measure 180 degrees. They are frequently encountered in various geometric shapes and real-life situations, such as in triangles, rhombi, parallelograms, and everyday objects like doors and scissors.

### Can a triangle have more than one obtuse angle?

No, a triangle cannot have more than one obtuse angle. The sum of the interior angles of a triangle is always 180 degrees. If a triangle were to have more than one obtuse angle, the sum of the angles would exceed 180 degrees, which would violate the fundamental property of triangles. A triangle can have only one obtuse angle, which makes it an obtuse triangle, with the other two angles being acute angles.

### Are the opposite angles of a parallelogram with obtuse angles also obtuse?

Yes, the opposite angles of a parallelogram with obtuse angles are also obtuse and have the same degree measurement. In a parallelogram, opposite angles are always equal. If one angle of a parallelogram is obtuse, the opposite angle must also be obtuse. The other pair of opposite angles in the parallelogram will be acute angles, with their degree measurements adding up to 180 degrees.

### Can a square have an obtuse angle?

No, a square cannot have an obtuse angle. A square is a specific type of quadrilateral in which all four sides are of equal length, and all four angles are right angles. Each angle in a square measures exactly 90 degrees, which is the defining characteristic of a right angle. Since an obtuse angle measures more than 90 degrees, it is not possible for a square to have an obtuse angle.