It is given that RM and RN are the two tangent segments of a circle with centre O. Let OR be the segment and from ΔMOR and ΔNOR,
MR=NR( Tangent segments of circle are always equal)
OM=ON(Radius of the circle)
OR=OR ( Common)
Therefore by SSS rule of Congruency,ΔMOR≅ΔNOR
⇒ By CPCT,
∠MRO=∠NRO
Thus, the segment OR bisects the angle MRN
Hence proved.