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A chord of length 8 cm is drawn at a distance of 3 cm from the center of a circle. Calculate the radius of the circle.

Circles

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Answer

A chord of length 8 cm is drawn at a distance of 3 cm from the center of a circle. Calculate the radius of the circle. Circle, Concise Mathematics Solutions ICSE Class 9.

Let AB = 8 cm be the chord of the circle with center O.

We know that,

Perpendicular from center to chord, bisects the chord.

∴ AC = AB2=82\dfrac{AB}{2} = \dfrac{8}{2} = 4 cm.

In right angled triangle OAC,

By pythagoras theorem,

⇒ Hypotenuse2 = Perpendicular2 + Base2

⇒ OA2 = OC2 + AC2

⇒ OA2 = 32 + 42

⇒ OA2 = 9 + 16

⇒ OA2 = 25

⇒ OA = 25\sqrt{25} = 5 cm.

Hence, radius of circle = 5 cm.

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