Evaluating scalar products of two functions

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The discussion focuses on evaluating scalar products of two functions defined in a vector space, specifically calculating ##\braket{f|f} , \braket{f|g} , \braket{g|g}## using the integral definition of the scalar product. The functions involved are ##f(x) = sin^2(x)+cos(x)+1## and ##g(x) = cos^2(x)-cos(x)##, both of which lack imaginary components. Participants confirm that the approach of multiplying the functions and evaluating the integral is correct and straightforward. The conversation reassures that the simplicity of the method does not detract from its validity. Overall, the task is to apply basic integral calculus to find the required scalar products.
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Homework Statement
Find ##\braket{f|f} , \braket{f|g} , \braket{g|g}##.
Relevant Equations
integral, scalar product
I am to consider a basis function ##\phi_i(x)##, where ##\phi_0 = 1 ,\phi_1 = cosx , \phi_2 = cos(2x) ## and where the scalar product in this vector space is defined by ##\braket{f|g} = \int_{0}^{\pi}f^*(x)g(x)dx##

The functions are defined by ##f(x) = sin^2(x)+cos(x)+1## and ##g(x) = cos^2(x)-cos(x)##
My task is to find ##\braket{f|f} , \braket{f|g} , \braket{g|g}##.

Given that f(x) and g(x) have no imaginary parts, is this problem really as simple as multiplying these two functions and evaluating the integral? If so I have no trouble doing that, I guess I just want to make sure I understand correctly what the question is asking. I am pretty sure my thought process is correct but I am just a bit unsure because of how simple the approach is.
ψ
 
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guyvsdcsniper said:
Homework Statement:: Find ##\braket{f|f} , \braket{f|g} , \braket{g|g}##.
Relevant Equations:: integral, scalar product

I am to consider a basis function ##\phi_i(x)##, where ##\phi_0 = 1 ,\phi_1 = cosx , \phi_2 = cos(2x) ## and where the scalar product in this vector space is defined by ##\braket{f|g} = \int_{0}^{\pi}f^*(x)g(x)dx##

The functions are defined by ##f(x) = sin^2(x)+cos(x)+1## and ##g(x) = cos^2(x)-cos(x)##
My task is to find ##\braket{f|f} , \braket{f|g} , \braket{g|g}##.

Given that f(x) and g(x) have no imaginary parts, is this problem really as simple as multiplying these two functions and evaluating the integral? If so I have no trouble doing that, I guess I just want to make sure I understand correctly what the question is asking. I am pretty sure my thought process is correct but I am just a bit unsure because of how simple the approach is.
ψ
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First, I tried to show that ##f_n## converges uniformly on ##[0,2\pi]##, which is true since ##f_n \rightarrow 0## for ##n \rightarrow \infty## and ##\sigma_n=\mathrm{sup}\left| \frac{\sin\left(\frac{n^2}{n+\frac 15}x\right)}{n^{x^2-3x+3}} \right| \leq \frac{1}{|n^{x^2-3x+3}|} \leq \frac{1}{n^{\frac 34}}\rightarrow 0##. I can't use neither Leibnitz's test nor Abel's test. For Dirichlet's test I would need to show, that ##\sin\left(\frac{n^2}{n+\frac 15}x \right)## has partialy bounded sums...

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