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[tex] \psi_{x} (x) = N \sin k_{n} x [/tex] for 0 < x < a

where [tex] k_{n} = \frac{n \pi}{a} [/tex] and n = 1,2,3,...

Consider the Fourier sine series for the function f(x) on teh interval 0<x<a

[tex] f(x) = \sum_{n=1,2,3,...} c_{n} \psi_{n} (x) [/tex]

Showthat the coefficients of this series are given by

[tex] c_{n} = \frac{2}{a} \int_{0}^{a} \sin (k_{n} x) f(x) dx [/tex]

do i have to PROVE that the coefficients are given by Cn??

isnt the expression by Cn given by the definition of Cn from teh Foureir series?? Also why is the persiod a? If n was not 1 then the period would not be a, would it/?