dl= acsc de dE↑y 2= a cSc 1 2dl cOS 4. C 2 a csc de 0 4 2 2 兀EcSc (Sin 0,-sin 81) 4兀Eaθ a xθ 2 θ 1 l dl 0 dE yθ r a a =2 r 2 a csc θ2 dl = a cscθ θ 2 d 2 0 2 2 2 0 1 cos 4 1 csc cos 4 csc x dl dE r a d a           21 0 2 1 0 cos 4 (sin sin ) 4 Ex d a a              