Answers to those Homework Problems that you must
write up and turn in at recitation (i.e. the HW
problems not on the Mastering Physics web site)
will be posted here.
E1.  proof
P25. For both components, the magnitude turns out
    to be k(lambda)/R
E2.  proof
W72. proof
Suggested exercise from "Magnetic Field from Current Segments" Part E.
W68. (a) (pi/3)R²J_0
     (b) (mu0/6r)R²J_0
     (c) (mu0/2)rJ_0(1-(2r/3R))