Understanding and Applying Dirichlet's Conditions for |x| on [-\pi, \pi]

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In summary, the function |x| satisfies Dirichlet's conditions on [-\pi, \pi] if the following conditions are met: (i) The left and right hand limits at all points in the interval exist as finite numbers. (ii) The endpoints have existing left and right hand limits. (iii) The right and left hand derivatives at all points in the interval exist as finite numbers. (iv) The endpoints have existing right and left hand derivatives.
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How to show in details that the function |x| satisfies Dirichlet's conditions on \(\displaystyle [-\pi \pi]\).;

I know the Dirichlet's conditions, but facing problems to apply it on the given function.
 
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suvadip said:
How to show in details that the function |x| satisfies Dirichlet's conditions on \(\displaystyle [-\pi \pi]\).;

I know the Dirichlet's conditions, but facing problems to apply it on the given function.

Dirichlet's condition, I assume means what most books called piecewise $\mathcal{C}^1$.

Let $f:[a,b]\to \mathbb{R}$ be a function. Here is the definition of what it means for $f$ to be piecewise $\mathcal{C}^1$:

(i) Let $p\in (a,b)$, $\lim_{x\to p^+} f(x) \text{ and }\lim_{x\to p^-} f(x)$ both exist as finite numbers. We denote these numbers by $f(p+)$ and $f(p-)$ respectively and call them the left and right hand limits.

(ii) For $p=a,b$, the endpoints, we require that $f(a+)$ and $f(b-)$ to exist.

(iii) For every $p\in (a,b)$ we require that,
$$ f'(p+) = \lim_{x\to p^+} \frac{f(x) - f(p+)}{x-p} \text{ and }f'(p-) = \lim_{x\to p^-} \frac{f(x)-f(p-)}{x-p} $$
To both exist as finite numbers, we call these the right-hand and left-hand derivatives.

(iv) For $p=a,b$ we require for $f'(a+)$ and $f'(b-)$ to exist in the way defined above.

Which of these conditions can you verify?
 

FAQ: Understanding and Applying Dirichlet's Conditions for |x| on [-\pi, \pi]

What are Dirichlet's conditions?

Dirichlet's conditions are a set of mathematical rules used to determine whether a Fourier series converges to a particular function. They were developed by German mathematician Peter Gustav Lejeune Dirichlet in the 19th century.

How many conditions does Dirichlet's theorem have?

Dirichlet's theorem has three conditions: the function must be periodic, the function must have a finite number of discontinuities within each period, and the function must have a finite number of extrema within each period.

What is the purpose of Dirichlet's conditions?

The purpose of Dirichlet's conditions is to determine whether a Fourier series can accurately represent a given function. If all three conditions are met, then the Fourier series will converge to the original function.

What happens if a function does not meet Dirichlet's conditions?

If a function does not meet Dirichlet's conditions, then the Fourier series may not converge to the original function. This means that the Fourier series may not accurately represent the given function and may have significant errors.

Are Dirichlet's conditions necessary for a Fourier series to converge?

Yes, Dirichlet's conditions are necessary for a Fourier series to converge to a given function. If the conditions are not met, then the Fourier series may not converge or may not accurately represent the function.

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