Lines and Angles

Angles and Its Types

We come across angles in our everyday life. We see angels all around us, like the space between our fingers, also while crossing the roads. Have you observed the alphabet A? We can see three angles in this alphabet. Such angles are also found in the alphabets H, L and many more. We can see the angles in the rooms of our houses, school and offices. Let us now understand this better by studying the topic angles and types of angles in detail.

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What is an Angle?

Angle is the combination of two rays with a common endpoint. The symbol for an angle is ∠. The corner point of an angle is called the vertex of an angle. The two straight sides of the angle are called arms of the angle.

The angles which are measured anticlockwise from the base are something we call as positive angles.  The angles measured clockwise from the base are called as negative angles. The standard unit of measuring an angle is degree. It is denoted by °.

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Types of Angles

There are many different types of angles. Let us study them carefully.

1.  Right Angle

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

types of angles

2. Acute Angle

Have you observed the angle between the cuts on a pizza? Don’t you think it looks just similar to the acute angles? An angle that is less than a right angle and which measures less than 90° is an acute angle. Acute angle lies between 0 degrees and 90 degrees. In the figure given below, you can see the acute angle with measure less than 90°.

types of angles

3. Obtuse Angle

An angle which is more than a right angle and which measures greater than 90° is an obtuse angle. This angle lies between 90 degrees and 180 degrees. A door when kept wide open forms an obtuse angle. In the figure given below, you can see the obtuse angle with the measure of more than 90°.

types of angles

Other Types of Angles

  • Reflex Angle: A reflex angle is an angle which measures more than 180° but less than 360°.
  • Straight Angle: The straight angle is an angle whose measure is 180 degrees. It straight angle look like a straight line. They are collinear and opposite rays. When the thin book is kept open, we can see that the angle formed between the two pages is an example of the straight angle.
  • Adjacent Angle: Two angles are adjacent when they share a common side and a vertex.
  • Vertically Opposite Angles: Vertically opposite angles are the angles formed opposite to each other when two lines intersect.
  • Complementary Angles: Two angles are complementary when they add up to 90°
  • Supplementary Angles: Two angles are supplementary when adding up to 180°

Solved Examples for You

Question 1: There is three angle 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

  1. Acute angle
  2. Obtuse angle
  3. Right angle
  4. Straight angle

Answer : The correct option is C. One angle is right angle = 90°, the second angle is straight angle = 180°. As 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 Reflex angle.

Question 3: What is the angle?

Answer: Angle refers to the combination comprising of two rays having a common endpoint. Similarly, we use the symbol ∠ to denote an angle. Moreover, the vertex of an angle refers to the corner point of an angle. Further, we refer to the two straight sides of the angles as its arms.

Question 4: What are the positive and negative angles?

Answer: We refer to positive angles as one which we measure anti-clockwise from the base. Similarly, the angles which we measure clockwise from the base, we refer to these as negative angles. Further, we use the standard unit of the degree to measure an angle. Thus, we use the symbol of ° to denote it.

Question 5: Define a straight angle.

Answer: A straight angle refers to an angle that has a measure of 180 degrees. Thus, you can say that a straight angle resembles a straight line. Moreover, it is collinear and opposite rays. For instance, when you have a thin book and you keep that open, you will notice it forms an angle between the two pages which make up a straight angle.

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