hi karan,

see its nt a guess my friend, as u see abc will be an isosceles triangle so u know its median will also be a prependicular to a base and now frm circle's prespective we know that if we extend that isosceles trngle median bisector ,dats gonne be a radius why?? answer is prependicular drawn from the centre bisects the chord...a well known property ..hope this helps!!!!