Examples

 Example 1: Observe the measure of the angles and identify the type of angles for each figure.

Solution:

a) The given angle is equal to 40°. It is an acute angle because its measure is less than 90°.

b) The given angle is equal to 117°. It is an obtuse angle because its measure is greater than 90° but less than 180°.

c) The given angle is equal to 121°. It is an obtuse angle because its measure is greater than 90° but less than 180°.

d) The given angle is equal to 185°. It is a reflex angle because its measure is greater than 180° but less than 360°.

Example 2: Classify the following angles into acute angles, obtuse angles, right angles, or reflex angles.

a) 24°

b) 150°

c) 90°

d) 270°

Solution:

(a) 24° lies in between 0° and 90°, so it is an acute angle.

(b) 154° lies in between 90° and 180°, so it is an obtuse angle.

(c) 90° is known as the right angle.

(d) 270° lies in between 180° and 360°, so it is a reflex angle.

Example 3: Write true or false for the following statements:

a.) 180° < Reflex angle < 360°

b.) 0°< Obtuse angle < 90°

c.) The two rays which join at a common point to form an angle are called the arms of the angle.

Solution:

a.) True, 180° < Reflex angle < 360°

b.) False, 0°< Acute angle < 90°

c.) True, the two rays which join at a common point to form an angle are called the arms of the angle.