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

Let circle with centre O has two tangents AB and AC.
To prove
Construction Join AO, BO and OC
Proof
(Tangent at any point of the circle is perpendicular to the radius)
In and
(both
)
(radius of the circle)
(common)
By R.H.S congruency
Hence by CPCT :
Hence proved.