AP State Syllabus AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2 Textbook Questions and Answers.

AP State Syllabus 9th Class Maths Solutions 12th Lesson Circles Exercise 12.2

AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2

Question 1.
In the figure, if AB = CD and ∠AOB = 90° find ∠COD.
AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2 1
Solution:
‘O’ is the centre of the circle.
AB = CD (equal chords from the figure)
∴ ∠AOB = ∠COD
[ ∵ equal chords make equal angles at the centre]
∴ ∠COD = 90° [ ∵ ∠AOB = 90° given]

AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2

Question 2.
In the figure, PQ = RS and ∠ORS = 48°.
Find ∠OPQ and ∠ROS.
AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2 2
Solution:
‘O’ is the centre of the circle.
PQ = RS [given, equal chords]
∴∠POQ = ∠ROS [ ∵ equal chords make equal angles at the centre]
∴ In ΔROS
∠ORS + ∠OSR + ∠ROS = 180°
[angle sum property]
∴ 48° + 48° + ∠ROS = 180°
[ ∵ OR = OS(radii); ΔORS is isosceles]
∴ ∠ROS = 180° – 96° = 84°
Also ∠POQ = ∠ROS = 84°
∴ ∠OPQ = ∠OQP
[∵ OP = OQ; radii]
= \(\frac { 1 }{ 2 }\)[180°-84°] = 48°

AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2

Question 3.
In the figure, PR and QS are two diameters. Is PQ = RS ?
AP Board 9th Class Maths Solutions Chapter 12 Circles Ex 12.2 3
Solution:
‘O’ is the centre of the circle.
[ ∵ PR, QS are diameters]
OP = OR (∵ radii) .
OQ = OS (∵ radii)
∠POQ = ∠ROS [vertically opp. angles]
∴ ΔOPQ ≅ ΔORS [SAS congruence]
∴ PQ = RS [CPCT]