In Example 6-4, we did lots of calculations for obtaining vector magnetic potential vec(A) and magnetic flux
density vec(B). Please finish the two key calculations shown below.
(1) (del)/(delr)[(\mu _(0)I)/(4\pi )ln((\sqrt(L^(2)+r^(2))+L)/(\sqrt(L^(2)+r^(2))-L))]
(2) \int_(-L)^L (rdz^('))/((z^('2)+r^(2))^((3)/(2)))