(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Known formula:[tex]J_0(k\sqrt{\rho^2+\rho'^2-\rho\rho'\cos\phi})=\sum e^{im\phi}J_m(k\rho)J_m(k\rho')[/tex]

I can't derive to next equation which is [tex]e^{ik\rho\cos\phi}=\sum i^me^{im\phi}J_m(k\rho)[/tex]

2. Relevant equations

Can anyone help me? Thanks a lot!!

3. The attempt at a solution

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# Bessel function equivalence

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