Chapter 15. CIRCLES
Optional Questions and Answers for Algebraic Expressions and Polynomials [1 Mark]
CHECK YOUR PROGRESS 3.1
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Long Questions and Answers for Algebraic Expressions and Polynomials [ 3 or 4 Mark]
CHECK YOUR PROGRESS 15.1
In questions 1 to 5, fill in the blanks to make each of the statements true.
1. In Fig. 15.25,
(i) AB is a ... of the circle.
(ii) Minor arc corresponding to AB is... .
Answer: (i) AB is a chord of the circle.
(ii) Minor arc corresponding to AB is APB .
2. A ... is the longest chord of a circle.
Answer: A diameter is the longest chord of a circle.
3. The ratio of the circumference to the diameter of a circle is always ... .
Answer: The ratio of the circumference to the diameter of a circle is always constant .
4. The value of π as 3.1416 was given by great Indian Mathematician... .
Answer: The value of π as 3.1416 was given by great Indian Mathematician aryabhata-I
5. Circles having the same centre are called ... circles.
Answer: Circles having the same centre are called concentric circles.
6. Diameter of a circle is 30 cm. If the length of a chord is 20 cm, find the distance of the chord from the centre.
Solution: Here, AB = 30 cm , OA=OB =OC=AB2=302=15 cm
, CD=20 cm and CM=DM=12CD=202=10 cm
Photo
In ∆OCM , we have
OM2+CM2=OC2
⇒OM2=OC2-CM2
⇒OM=152-102=225-100=125=5²×5
⇒OM=55cm
Therefore, the distance of the chord from the centre is 55cm .
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