In the figure AB is a tangent to a circle with centre O. AP is a chord of the circle such that AP=PQ. Prove that OA2 =OB*OQ?

Dear Student,

In OAQ and OQP,OA=OP  radius of the circleOQ=OQ commonAQ=PQ  GivenOAQOQPAQO=PQOBut AQO+PQO=180AQO=PQO=90Now,In right OAB,OB2=OA2+AB2OB2=OA2+BQ2+AQ2     In right AQB, AB2=BQ2+AQ2OB2=OA2+OB-OQ2+AO2-OQ2        In right AQO, AQ2=AO2+OQ2OB2=OA2+OB2+OQ2-2OB OQ+AO2-OQ2OA2=2OB OQHence Proved.
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