Consider the current loop in the figure below. Figure: http://east.ilrn.com/graphing/bca/user/appletImage?dbid=1450953670 Determine the magnetic field (in terms of a, I and d) at the origin. So I will use mu as the permeability of free space. Since the two vertical wires have opposite directions in current they cancel out, right? If so, then all I have to calculate is the horizontal wire. Well...I use the biot-savart law, but can't seem to get the correct answer. My answer is ((mu*I)/(4*pi*d))*(2*cos(pi/4)). Did I apply the law wrong or am I just totally wrong? Any help would be great, Thx!