Answer :
Case I. When the two chords are on the same side of the centre

Given: OM ⊥ AB
∴ M is the mid-point of AB. (∵ The perpendicular from the centre of a circle to a chord bisects the chord)
BM = AM =
AB =
(6) = 3 cm
Given: ON ⊥ CD
∴ N is the mid-point of CD. (∵ The perpendicular from the centre of a circle to a chord bisects the chord)
∴ DN = CN =
CD =
(8) = 4 cm
In right triangle OMB,
OB2 = OM2 + MB2 ( By Pythagoras Theorem )
= (4)2 + (3)2
= 16 + 9 = 25
⇒ OB =
= 5 cm
∴ OD = OB = 5 cm ( Radii of a circle)
In right triangle OND,
OD2 = ON2 + ND2 (By Pythagoras Theorem)
⇒ (5)2 = ON2 + (4)2
⇒ 25 = ON2+16
⇒ ON2 = 25-16
⇒ ON2 = 9
⇒ ON =
= 3 cm
Hence the distance of the other chord from the centre is 3 cm.
Case II. When the two chords are on the opposite sides of the centre
As in case I
ON = 3 cm.

Given: OM ⊥ AB
∴ M is the mid-point of AB. (∵ The perpendicular from the centre of a circle to a chord bisects the chord)
BM = AM =


Given: ON ⊥ CD
∴ N is the mid-point of CD. (∵ The perpendicular from the centre of a circle to a chord bisects the chord)
∴ DN = CN =


In right triangle OMB,
OB2 = OM2 + MB2 ( By Pythagoras Theorem )
= (4)2 + (3)2
= 16 + 9 = 25
⇒ OB =

∴ OD = OB = 5 cm ( Radii of a circle)
In right triangle OND,
OD2 = ON2 + ND2 (By Pythagoras Theorem)
⇒ (5)2 = ON2 + (4)2
⇒ 25 = ON2+16
⇒ ON2 = 25-16
⇒ ON2 = 9
⇒ ON =

Hence the distance of the other chord from the centre is 3 cm.
Case II. When the two chords are on the opposite sides of the centre

ON = 3 cm.
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