Pratibha Patil today trounced NDA-backed Bhairon Singh Shekhawat by an unexpectedly higher margin to become the first woman President of India.The UPA-Left nominee defeated Shekhawat with a margin of vote value of over three lakh "" about 10,000 more than expected by her Congress poll managers "" thanks to cross-voting in her favour in some states.As bouquets poured into Patil's Delhi home and Congress activists burst crackers and danced to drum beats, the BJP camp was gloomy also because of the cross voting by party legislators in key states of Gujarat and Chhattisgarh.Following his humiliating defeat, B S Shekhawat today announced he would resign from the post of the Vice-President.The Congress had been seeking Shekhawat's resignation during the campaign for the Presidential election. Patil's margins also rose because of the cross-voting from AGP in Assam.In the final tally, Patil had bagged a vote value of 6,38,116 while Shekhawat got 3,31,306 in an electoral college of 10.98 lakh. Patil has got 65.82 per cent of the valid votes.She had received votes of 442 MPs as against 232 of Shekhawat.