Types of angles

Although we may not realize it, we constantly encounter angles in our daily lives. We always see them around us, from the space between our fingers, even when we cross the road or enter the rooms of our houses, schools and offices. To get an understanding of what angles are and what types are , keep reading our informative article.

What is an angle?

Angle is the combination of two lines with a common end point (The symbol for an angle is ∠). The straight lines of the angle are called the sides and the point located at the corner where the latter meet is called the vertex.

The angles that are measured counterclockwise from the base are what we call positive angles . Angles measured clockwise from the base are called negative angles . The standard unit of measurement for an angle is the degree (denoted by °).

Types of angles

There are many different types of angles:

1. Right angle

Right angles can be seen anywhere you look around. Have you seen houses, buildings, and other structures incorporate the correct angle into their construction? What is a right angle? Well, the angles that measure equal to 90 ° are the right angles . In the figure below, you can see the right angle with a measure of 90 °.

2. Acute angle

Have you observed the angle between the slices in a pizza? Don’t you think they look like acute angles? An angle that is less than a right angle and is less than 90 ° is an acute angle . The acute angle is between 0 degrees and 90 degrees. In the figure below, you can see the acute angle with a measurement less than 90 °.

3. An obtuse angle

An angle that is more than a right angle and that measures more than 90 ° is an obtuse angle . This angle is between 90 degrees and 180 degrees . A door when held open forms an obtuse angle. In the figure below, you can see the obtuse angle with the measure over 90 °.

4. Plain angle

An angle that measures 180 ° is known as a straight angle . This looks like a flat straight line and is therefore called a straight angle. The following figure will clarify the concept.

5. Concave angle

An angle that measures more than 180 degrees but less than 360 degrees is known as a concave angle . A reflex angle is assumed to be a complementary angle to the acute angle and is on the other side of the line. The following figure illustrates the reflex angle.

Geometry finds its basis in angles. From basic closed shapes to difficult trigonometry questions, angles are part of every chapter. Understanding this surely helps to hone your knowledge of geometry and trigonometry.

6. Zero angle (null)

A zero angle (0 °) is an angle that is formed when both arms are in the same position.

7. Full angle

A full angle is equal to 360 °. 1 revolution is equal to 360 °.

Angle classification based on rotation

According to the direction of rotation, the angles can be classified into two categories;

  • Positive angles
  • Negative angles

Positive angles: Positive angles are the types of angles whose measurements are taken counterclockwise from the base.

Negative Angles: Negative angles are measured clockwise from the base.

Other types of angles

In addition to the angles discussed above, there are other types of angles known as even angles. They are so called because they appear in pairs to show a certain property. These are:

  • Adjacent angles: they have the same vertex and arm.
  • Complementary angles : even angles that add up to 90º.
  • Supplementary angles : even angles whose sum of angles is equal to 180º.
  • Vertically opposite angles : Vertically opposite angles are equal
  • Alternate Interior Angles: Alternate interior angles are even angles formed when a line intersects two parallel lines. Alternate interior angles are always equal to each other.
  • Alternate Exterior Angles – Alternate exterior angles are simply vertical angles of alternate interior angles. The alternate exterior angles are equivalent.
  • Corresponding Angles: Corresponding angles are even angles formed when a line intersects a pair of parallel lines. The corresponding angles are also equal to each other.

We saw a brief description of the different types of angles. Next we will leave you a series of exercises so that you can practice from the comfort of your home.

Exercises on angles

Question 1: There are three angles formed at a point. If one of the angles is the right angle, the second angle is the straight angle, then the third angle must be

  • Acute angle
  • an obtuse angle
  • Right angle
  • Plain angle

Answer: The correct choice is C. One angle is right angle = 90 °, the second angle is straight angle = 180 °. Since we know that the sum of the angle at a point is 360 °, therefore the third angle is 360 ° – (180 + 90) = 90 ° = 90 ° is a right angle.


Question 2: What are the 5 types of angles?

Answer: The 5 types of angles are acute angle, right angle, obtuse angle, straight angle, and concave angle.

Question 3: What is an angle?

Answer: An angle refers to the combination of two sides that have a common end point. Similarly, we use the symbol ∠ to denote an angle. Also, the vertex of an angle refers to the point on the corner where the sides meet. Each line that forms an angle is known as a side (or arm).


Question 4: What are the positive and negative angles?

Answer: Positive angles are those that we measure counterclockwise from the base. Similarly, the angles that we measure clockwise from the base, we call negative angles. Also, we use the standard unit of degree to measure an angle. Therefore, we use the symbol for ° to denote it.

Question 5: Define what is a straight angle.

Answer: A right angle refers to an angle that has a measure of 180 degrees. Therefore, you can tell that it looks like a straight line. Also, it is collinear and opposite sides. For example, when you have a thin book and you keep it open, you will notice that it forms an angle between the two pages, that is the shallow angle

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