What Are The Types of Angles – Acute? Here’s Everything You Need To Know

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How do you define acute angles? An acute angle is smaller than 90˚. An obtuse angle, on the other hand, is acute, which is more than 90 degrees. Beginning from the importance of understanding angles in Maths, we’ll describe the classifications and measurements of each Angle.

How do you define an angle?

First, what exactly does an angle mean? We must understand angles before we begin considering acute angles.

The term “angle” refers to geometry. An angle is defined as the shape formed by two rays coming together at a common point. Two rays- or lines that intersect at the point of intersection are referred to as the ‘arms of an angle’. An angle is nothing but the measurement of a turn, which is measured in deg or degrees. 

You can determine the dimensions of an angle with the protractor. There are 360degree of Angle in one full turn. 

The point where the end is located is known in the term “vertex. It’s something like the ruler. It’s a semicircular piece of transparent, flat plastic that has lines drawn on it. It is possible to line up the lines using an angle to determine the angles.

The term “angle” originates from the Latin word “angulus,” which means “a small bend”. The concept of an angle was first used by Eudemus, which defined Angle as an inclination from straight lines.

What are the five types of angles?

Several kinds of angles differ in both size and measurement. Students need to understand the different angles.

The term “Acute angle” refers to angles smaller than 90°.

  • Obtuse angles are over 90 degrees but not more than 180 degrees.
  • Reflex angles are higher than 180 degrees.
  • Right angles are precisely 90 degrees in measurement.
  • Straight angles are precisely 180 degrees which is why they are straight lines.
  • Complete angles are full angles that are exactly 360° in length, so they are also a circle.

What is an acute angle?

Among the types of angles, in the previous section, we described that an angle measuring not more than 90 degrees, i.e. lower than an angle of right angles, is the term used to describe an acute angle. The most common examples of the acute angle degree are 63°, 31°, 44°, 68°, 85° and 83°. Thus the acute Angle falls within the range of 0° to 90° or less. 

You can recall the meaning of an acute angle by making use of this mnemonic. 

We know that angles more than 0° but less than 90° are referred to as acute angles in geometrical terms. Thus, 45°, 5°, 28°, 49° and 89° are all instances of acute angles.

Here are some real-world examples of acute angles.

  • Slices of watermelon when cut into smaller pieces.
  • Some examples of angles formed between the hour’s hand and the minute’s hand on the clock.
  • Beaks of birds when it is fully open.
  • The Angle develops when the mouth of a crocodile’s fully open.

What is an Obtuse Angle?

An obtuse angle within Geometry defines any angle greater than 90 degrees, but less than 180 degrees is referred to as an obtuse angle. In terms of definition, an obtuse angle can be described as an angle that lies between the right and straight Angle. 

The examples of obtuse angle degrees are 165°,135°,110°,189° and 91°. Thus the obtuse Angle falls within the ranges of 90° up to under 180°.

What are Reflex Angles?

The reflex angle is 360 degrees and is the principal Angle like acute Angle or right Angle and the obtuse Angle. It is more than straight angles. This is why,

  • Reflex angle = 180 degrees Acute angle
  • Reflex angle = 180 degrees Right angle
  • Reflex angle = 180 degrees Obtuse angle

To determine the reflex angle XYZ, you must follow the steps as outlined below.

  • Step 1: Set your protractor’s centre on the centre and align it to the line running through zero degrees.
  • Step 2: Find the point at which 180 degrees completes and mark it.
  • Step 3: Now, measure the remaining portion of the Angle, starting at 180 degrees until the 2nd line.
  • Step 4: Once the Angle is more in comparison to 180 degrees, then add it to 180 degrees to calculate the Angle of reflex needed.
  • Step 5: Now, you can check the measured Angle by taking the internal Angle and subtracting this from the Angle of 360 degrees. This is a different method to calculate reflex angles. It is also a great tool to confirm.    

What are the Right Angles?

The term “right angle” refers to a 90 degrees angle. When two rays meet and create 90-degree angles or are perpendicular with each other at the point of junction, they will form by a right angle. They take the form of the letters “L”. In the figure below, the rays AB and BC create a right angle ABC.

What exactly is a Straight Angle?

A Straight angle measures exactly 180 degrees. It is referred to as straight because it appears to be straight lines. In essence, according to angles definition in math, when two rays of light are joined from one end to the other, creating an angle, it creates the straight Angle. 

Straight angles may consist of a variety of angles, as long as they total 180 degrees.

What is the definition of Complete Angles?

If, after a complete rotation, the final ray is in alignment with the original or incident ray, The Angle thus formed is called full Angle. Other names are full Angle as well as the term “round angle. 

The Angle is equivalent to 2p radians, which is 360 degrees and corresponds to the centre angle in the complete circle. The four straight angles (or straight angles) create an entire angle. The Angle is comparable with a zero angle, but the difference lies in the extent of rotation.


Angles are a crucial component of the curriculum of every country. They are essential strands of Maths to master and retain for children and carry with them when they come in the future.

Inviting children to visualise and conceptualise angles can be fun and engaging. It is also essential to their understanding of the subject. It can help them improve their skills, not just in this subject but also in related ones. It is helpful in subjects such as Design and Technology or Science.

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