1. The problem statement, all variables and given/known data A short, straight wire segment of length l carries current I and is oriented so that it makes an angle of 30° with the horizontal. Point P is a distance r below the wire segment. Which expression below is the best approximation for the magnetic field caused by the wire segment at point P? http://online.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?courses/phys212/oldexams/exam2/fa09/fig15.gif [Broken] (a) (μoIlcos30°) / (4π^2) (b) (μoIlsin30°) / (4π^2) (c) (μoIl) / (4π^2) 2. Relevant equations dB = (μo Idl x r(unit vector)) / (4πr^2) 3. The attempt at a solution It seems I have to integrate to get the answer, however the geometry behind this problem is really confusing me. I believe I have to integrate r from when it touches the begining of the wire segment to the end of the wire segment, however I can't figure out how to manipulate the Biot-Svart law to do that. This is what I have so far: (μo I)/(4π) = S sin(theta)ds/r^2 (S = integral :p) Now, what do I do with ds? Can anyone help me out, help would be greatly appreciated :]! Btw π = pi and μo = mu(0), dont know if you can tell.