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Question -

Two tangents segments PA and PB are drawn to a circle with centre O such that тИаAPB = 120┬░. Prove that OP = 2 AP. [CBSE 2014]



Answer -

Given : From a point P. Out side the circle with centre O, PA and PB are tangerts drawn and тИаAPB = 120┬░
OP is joined To prove : OP = 2 AP
Const: Take mid point M of OP and join AM, join also OA and OB.
┬а
Proof : In right тИЖOAP,
тИаOPA = 1/2 тИаAPB = 1/2 x 120┬░ = 60┬░
тИаAOP = 90┬░ тАУ 60┬░ = 30┬░
M is mid point of hypotenuse OP of тИЖOAP
MO = MA = MP
тИаOAM = тИаAOM = 30┬░ and тИаPAM = 90┬░ тАУ 30┬░ = 60┬░
тИЖAMP is an equilateral triangle
MA = MP = AP
But M is mid point of OP
OP = 2 MP = 2 AP
Hence proved.

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