Exercise 4.2

Exercise 4.2

1. Use any number of the given dots to make different angles.

2. Name the vertex and sides that form each angle.

3. Pick out the Right angles from the given figures.

Answer: Right angles = i, iii and v 

4. Pick out the Acute angles from the given figures.

Answer: Acute angles = (i), (iii) and (iv)

5. Pick out the Obtuse angles from the given figures.

 Answer: Obtuse angles = (i) & (ii)

6. Name the angle in each figure given below in all the possible ways.

(i) ∠LMN, ∠NML ∠M

(ii) ∠PQR, ∠PQP ∠Q

(iii) ∠MNO, ∠ONM ∠N

(iv) ∠TAS, ∠SAT ∠A

(v) ∠XYZ, ∠ZYX ∠Y

(vi) ∠ADB, ∠BDA ∠D

7. Say True or False.

(i) 20° and 70° are complementary. Answer: True

(ii) 88° and 12° are complementary. Answer: False

(iii) 80° and 180° are supplementary. Answer: False

(iv) 0° and 180° are supplementary. Answer: True

8. Draw and label each of the angles.

(i) ∠NAS

(ii) ∠BIG

(iii) ∠SMC

9. Identify the types of angles shown by the hands of the given clock.

(i) Obtuse angle

(iv) Zero angle

(iii) Straight line

(iv) Actute angle

(v) Right angle

10. Find the supplementary / complementary angles in each case.

(i) ∠ABD = 180° − ∠CBD

= 180°− 25°

∠ABD = 155°

(ii) ∠ABD = 90° − ∠CBD

= 90° − 30° = 60°

∠ABD = 60°

(iii) ∠ABD = 90° − ∠CBD

= 90° − 46° = 44°

∠ABD = 44°

(iv) ∠ABD = 180° − ∠CBD

= 180° − 67° = 113°

∠ABD = 113°

Objective Type Questions

11. In this Figure, which is not the correct way of naming an angle?

(a) ∠Y

(b) ∠ZXY

(c) ∠ZYX

(d) ∠XYZ

Answer: (b) ∠ZXY

12. In this Figure, ∠AYZ = 45°. If point ‘A’ is shifted to point ‘B’ along the ray, then the measure of ∠BYZ is ___________.

(a) more than 45°

(b) 45°

(c) Less than 45°

(d) 90°

Answer: (c) Less than 45°

Answers:

Exercise 4.2

3) i), iii), v) are right angles

4) i), iii) and iv) are acute angles

5) i), ii) are obtuse angles

6) i) ∠LMN, ∠NML, ∠M

ii) ∠PQR, ∠RQP, ∠Q

iii) ∠MNO, ∠ONM, ∠N

iv) ∠TAS, ∠SAT, ∠A

v) ∠XYZ, ∠ZYX, ∠Y

vi) ∠ADB, ∠BDA, ∠D

7) i) True ii) False iii) False iv) True

9) i) Obtuse angle ii) Zero angle iii) Straight angle iv) Acute angle v) Right angle

10) i) 155˚ ii) 60˚ iii) 44˚ iv) 113˚

11) b) ∠ZXY c) 45˚