Page 197 - ICSE Math 6

EXERCISE 18.1

1. Using the adjoining figure, name the following.
(a) Centre A S

(b) Tangent O
B P
(c) Diameter

(d) Three radii R
(e) Point of contact

2. What is the length of the largest chord of a circle of radius 6 cm?
3. Using the adjoining figure, fill in the blanks. D

(a) If OA = 3 cm, OB = ________. C O
(b) The shaded region AOB is a minor ________. Q R

(c) The shaded region bounded by chord CD is a minor ________. A B S
(d) The points lying in the interior of the given circle are ________ and ________.
(e) The points R and S lie in the ________ of the circle.

4. In a circle with radius r cm,

(a) the length of the diameter is ________ cm
(b) the length of the largest possible chord is________ cm
5. If the centre of a circle is at point A and its radius is 7.5 cm, then point P will lie in:

(a) the ________ of the circle, when AP = 7.6 cm
(b) the ________ of the circle, when AP = 5 cm

6. The length of the diameter of a circle is 9 cm. Find the length of its radius.
7. The point A lies on the circumference of a circle with diameter 10 cm. If O is the centre of the
circle, then the length of OA is ________.

Construction of Circles

To construct a circle of given radius

Let’s draw a circle with centre at O and radius 5 cm. To do so,
follow the steps given below.

Step 1: Place a compass on a ruler to measure 5 cm.
Step 2: Mark a point O as the centre of the circle.
O 5 cm
Step 3: Place the pointed end of the compass at O.
Step 4: Rotate the pencil end of the compass to draw a circle
with centre at O and radius 5 cm.

To construct a circle with given line segment as a diameter

Let’s draw a circle with line segment AB of length 8 cm as the diameter. A 8 cm B

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