According to the figure we need to prove that AT=BTWe know thatAngle of incidence = Angle of reflectionSo we get∠ACN=∠DCN..(1)We know that AB∥CN and AC is the transversalFrom the figure we know that ∠TAC and ∠ACN are alternate angles∠TAC=∠ CAN(2)We know that AB∥CN and BD is the transversalFrom the figure we know that ∠TBC and ∠DCN are corresponding angles∠TBC=∠DCN..(3)By considering the equation (1),(2) and (3)We get∠TAC=∠TBC(4)Now in △ACT and △BCT∠ATC=∠BTC=90∘CT is common i.e. CT=CTBy AAS congruence criterion△ACT≅△BCTAT=BT(c.p.c.t)Therefore, it is proved that the image is as far behind the mirror as the object is in front of the mirror.