- #1

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[tex]\vec A=\frac{\mu I}{4\pi}\oint\frac{e^{-j\beta R_1}}{R_1}dl'[/tex]

After a few steps, the equation becomes:

[tex]\vec A=\frac{\mu I}{4\pi}e^{-j \beta R}\left[ (1+j\betaR)\oint\frac{dl'}{R_1}-j\beta\oint dl'\right][/tex]

The Book claim the second integral obviously vanishes!!!

I don't understand this. For a small loop, ##dl'=rd\phi##

[tex]\oint dl'=\int_0^{2\pi}rd\phi=2\pi r[/tex]

That is not zero by any stretch. Can anyone explain this?

thanks