The radius of the circle is 15 cm and the length of one of the chords is 18cm. Find the distance of the chord from the centre.
Answer
Verified
Hint: Draw a perpendicular from the center to the chord of the circle and use the property of the circle that says a perpendicular drawn from the centre of the circle to the chord bisects the chord.
Complete step-by-step answer: Let AB=18cm is the chord of the circle as given in the question And OB=15cm is the radius of the circle. Let OM be a perpendicular drawn from the centre of the circle to the chord. Let OM=x cm Since the perpendicular drawn on a chord from the centre of the circle bisects the chord (property of a circle) $ \Rightarrow $ MB=9cm Thus in the right angled triangle OMB, Using Pythagoras theorem we get, $O{B^2} = O{M^2} + M{B^2}$ $ \Rightarrow {(15)^2} = {x^2} + {(9)^2}$ $ \Rightarrow 225 = {x^2} + 81$ $ \Rightarrow {x^2} = 144$ $ \Rightarrow x = 12cm$ Thus the distance of the chord from the center of the circle is 12cm.
Note: It is very important in such questions to realize that we have to draw a perpendicular from the centre to the chord or else the property will not be applicable.
No right angled triangle is formed in such a case and hence is difficult to solve the question.
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