how can to prove this formule?

hi freinds
how can to prove this formule?
I(in)=I(0)sin(kL/2) when (z=0) in chapter4 page(160) balanis
please guide me?

i upload this part of antenna theory by balanis in rapidshare please guide me:
http://rapidshare.de/files/9951495/P...ine_A.pdf.html

hi,

I thought it's obvious from the graph (fig. 4.10), isn't it?

The equations 4-56 give the current distribution on any dipole and since the current at both ends are zero (since it's open-circuit) , for multiple lamda length of dipole, the current at the input is always zero.

Hope this helps.