# Index Introduction of angle Types of angles Exercise Index Introduction of angle Types of angles Exercise Yesterday we have studied about the angles. Today, we will study about the types of angles. Before continuing today's class we will discuss little bit about the angle. In mathematics, if two rays start from the same point, the figure so formed is called an angle. Examples -

Home Exit Next A m ar (Vertex) B arm C Above fig. shows angle ABC.

The point where the rays intersect is called the vertex of the angle. Here B is vertex. The two rays are called the arms of the angle. Here BA and BC are arms of angle ABC. Home Exit Back Next TYPES OF ANGLES There are five types of angles:1) 2) 3) 4)

5) Acute angle Right angle Obtuse angle Straight angle Reflex angle Home Exit Back Next Acute angle

Acute angle- An angle whose measure is more than 0 but less than 90 is called an acute angle. A O 60 B Given angle AOB measures 60 , which is less than 90 . So, it is an acute angle. Home Exit

Back Next Right angle-An angle whose measure is 90 is called a right angle. P O Given angle POQ measures 90 . So, it is a right angle. Home Exit

Q Back Next Obtuse angle An angle whose measure is more than 90 but less than 180 is called an obtuse angle. P 120 Q R

Given angle PQR measures 120 , which is more than 90 but less than 180 . So, it is an obtuse angle. Home Exit Back Next Straight angle An angle whose measure is 180 is called a straight angle. 180 B

O D Given angle BOD measures 180 . So, it is a straight angle. Home Exit Back Next Reflex angle An angle whose measure is more than 180 but less than 360 is called a reflex angle.

225 Q R P Given angle PQR measures 225 . So, it is a reflex angle. Home Exit Exit Back Next

Exercise 1) An angle whose measure is between 0 and 90 is called angle. (a) acute (b) right (c) obtuse Home Exit Back Next 2) An angle whose measure is 90 is called

angle. (a) acute (b) right (c) obtuse Home Exit Back Next 3) An angle whose measure is more than 90 but less than 180 is called

angle. (a) acute (b) right (c) obtuse Home Exit Back Next 4) A reflex angle is always greater than but less than 360 .

(a) 0 (b) 90 (c) 180 Home Exit Back Next 5) Which of the following is an acute angle(a) 45 (b) 120 (c) 305 Home Exit

Back Next 6) What is the measure of straight angle(a) 90 (b) 180 (c) 360 Home Exit Back Next 7) Which of the following is reflex angle(a) 150 (b) 60

(c) 320 Home Exit Back