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**1. The problem**

I have a problem grasping what the point of the sifting property of the Dirac function is.

It isolates the value at a point in a function, right?

Doesn't just substituting that point into the function do exactly the same thing?

## Homework Equations

__Sifting poperty:__

if [itex]f(t)[/itex] is continuous at [itex]t=a[/itex] then

[itex]\int_{-∞}^∞f(t)δ(t-a)dt= f(a)[/itex]

from: Glyn James, Advanced Modern Engineering Mathematics (3rd Ed), Section 2.5, p.155