i knw the pics not tht clear but its like tht one in resnick halliday........u have to find the magnetic field at pt. P.....here the arrow shows the direction of the current. here theta and the distance of pt.P frm the circular arc keep varying .... while the magnetic field due to both straight wires comes to be zero....... wat do i do ????? pls guys its a piece of cake 4 u all..............reply and get rated.....if a person tell the answer by a differnt method he too will get rated...........