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Question
In followinf fig., two concentric circles with centre 0 are of radii 5 cm and 3 cm. from an external point P, tangents PA and PB are drawn to these circles. If AP = 12cm, find BP.
Solution
∠ OAP = ∠ OBP = 90° (radius is .l to tangent at the point of contact)
In right Δ OAP ,
OP2 = OA2 + AP2
OP2 = 52 + 122 = 25+ 144= 169
OP = 13 cm
In right Δ OBP,
OP2 = OS2 + BP2
BP2 = 132 -32
BP2 =169 - 9 = 160
BP = `4 sqrt 10` cm
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