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| Dirac delta function integral |
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| Cujo:
I have no idea how to solve this Dirac delta function integral. So I would like some help please? :) |
| ataradov:
Is delta prime in this notation a standard Dirac function, or does the prime means something here? If it is a plain Dirac function, then it would be exp(5*0). In general an integral from a to b of f(x)*delta(x-c) is f(c) for a < c < b, 1/2*f(c) if c == a or c == b, or 0 otherwise. |
| Cujo:
--- Quote from: ataradov on March 21, 2021, 04:39:10 am ---Is delta prime in this notation a standard Dirac function, or does the prime means something here? If it is a plain Dirac function, then it would be exp(5*0). In general an integral from a to b of f(x)*delta(x-c) is f(c) for a < c < b, 1/2*f(c) if c == a or c == b, or 0 otherwise. --- End quote --- I think its the derivative of the delta function? The question doesn't say. It just says solve the integrals with no context. |
| ataradov:
I'm not sure if it apples to the Dirac function (partially because it is not really a function), but there is a thing where int(-inf, +inf) [f(x)*g'(x)dx] = -int(-inf, +inf) [f'(x)*g(x)dx]. I'm also not sure how this translates to definite integrals. But that may be at least direction for reseach. |
| ejeffrey:
Huh. I always thought the dirac delta function was non-differentiable but according to wikipedia you can define a differential distribution by integrating by parts the definition of the delta function. https://en.wikipedia.org/wiki/Dirac_delta_function#Distributional_derivatives If you evaluate that formula you get -5 * exp(5*t) | t=0 = -5 |
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