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The lengths of the two tangents segments to a circle drawn from an external point are equal.

The lengths of the two tangents segments to a circle drawn from an external point are equal. 


Given: Seg PA and seg PB are tangents.
To Prove: Tangent PA Tangent PB



Solution:
In ∆ AOP and ∆ BOP,
∠ A = ∠ B = 900 [∵ Radius is perpendicular to the tangent]
∴ Hypotenuse OP ≅ Hypotenuse OP    [ common side]
Side OA ≅ Side OB [Radii of same circle]
∴ ∆ AOP ≅ ∆ BOP    [ By Hypotenuse side test for congruency]
∴ Tangent PA ≅ Tangent PB  [C.S.C.T.]