Question

Angle ABC in the following figure is a/an

(a) acute angle
(b) obtuse angle
(c) reflex angle
(d) straight angle

Answer 1

Hint: We will look at the definition of an angle. There are various types of angles. We will list the types of angles and their definitions. After that, we will look at the figure and verify the condition satisfied by the angle shown in the figure. We will check the definitions of the types of angles and classify the angle in the figure according to its properties.

Complete step by step answer:
An angle is defined as the figure formed by two rays that share a common endpoint. This common endpoint is known as the vertex of the angle and the two rays are called the arms of the angle. With respect to the measurement of angle, we can classify the angles into various types.
If the angle lies between $0{}^\circ $ and $90{}^\circ $, then we call it an acute angle. The angle that measures exactly $90{}^\circ $ is called a right angle. The angle which lies between $90{}^\circ $ and $180{}^\circ $ is called an obtuse angle. A straight angle is an angle that measures exactly $180{}^\circ $. If the angle lies between $180{}^\circ $ and $360{}^\circ $, then we call it a reflex angle.
In the figure, we can see that the given angle lies between $180{}^\circ $ and $360{}^\circ $. Therefore, we can say that the angle shown in the figure is a reflex angle. Hence, the correct option is (c).

Note:
 We should be aware of all types of angles and their definitions. Apart from the types mentioned above, we also have the concept of a dihedral angle. A dihedral angle is defined as the angle between two intersecting planes. This type of angle is generally used in chemistry to express the angle between two planes passing through two sets of three atoms.