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In the following figure, AD is a straight line. OP ⊥ AD and O is the centre of both the circles. If OA = 34 cm, OB = 20 cm and OP = 16 cm; find the length of AB.

In the following figure, AD is a straight line. OP ⊥ AD and O is the centre of both the circles. If OA = 34 cm, OB = 20 cm and OP = 16 cm; find the length of AB. Circle, Concise Mathematics Solutions ICSE Class 9.

Circles

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Answer

From figure,

In right-angled triangle OBP,

By pythagoras theorem,

⇒ Hypotenuse2 = Perpendicular2 + Base2

⇒ OB2 = OP2 + BP2

⇒ 202 = 162 + BP2

⇒ 400 = 256 + BP2

⇒ BP2 = 400 - 256

⇒ BP2 = 144

⇒ BP = 144\sqrt{144} = 12 cm.

In right-angled triangle AOP,

⇒ Hypotenuse2 = Perpendicular2 + Base2

⇒ OA2 = OP2 + AP2

⇒ 342 = 162 + AP2

⇒ 1156 = 256 + AP2

⇒ AP2 = 1156 - 256

⇒ AP2 = 900

⇒ AP = 900\sqrt{900} = 30 cm.

From figure,

AB = AP - BP = 30 - 12 = 18 cm.

Hence, AB = 18 cm.

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