What is the basis for the inner product of functions?

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SUMMARY

The inner product of two functions f(x) and g(x) is defined as the integral \(\int_{a}^{b} f(x)g(x)dx\). This integral satisfies the properties of an inner product, confirming its validity as a definition. Additionally, when a positive integrable function w(x) is introduced, the inner product can be expressed as \(\langle f,g \rangle_{w} = \int_{a}^{b} f(x)g(x)w(x)dx\). For further details on the theoretical basis, refer to the resource provided at MathWorld.

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What is the proof that the inner product of two functions f(x) and g(x) is

[tex] \int_{a}^{b} f(x)g(x)dx[/tex]

Or is this actually a definition of the inner product for functions? If it is a definition, then what is it based on?

Thank you
 
Last edited:
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You've gotten it backwards:
That particular integral can be shown to fulfill the PROPERTIES OF AN INNER PRODUCT.

For your info, if w(x) is a positive integrable function, the following can also be shown to be an inner product:
[tex]<f,g>\mid_{w}=\int_{a}^{b}f(x)g(x)w(x)dx[/tex]
 

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