A triple integral involving deltas

1. Mar 4, 2009

skrtic

SOLVED

1. The problem statement, all variables and given/known data
evaluate the intergral

2. Relevant equations

sorry about how this is going to look don't know the language to display nicely and wouldn't take my copy and paste

all integrals are form -infinity to infinity

(x^2+32*z^2)*cos(y)*e^(x-4*z) delta(x-1) delta (y-pi) delta(z-.25) dx, dy dz

3. The attempt at a solution

well i looked at just the cos(y) part and got sin(y) then for the delta i plugged in pi since it is zero elsewhere and that gives me a 0 overall and since it is all mulitplication that makes the whole integral o?

thats my take.

never really understood teh delta's in integrals

Last edited: Mar 4, 2009
2. Mar 4, 2009

Avodyne

$$\int_{-\infty}^{+\infty}dx\,f(x)\delta(x-a) = f(a)$$

3. Mar 4, 2009

skrtic

ok. that makes sense. and kinda looks familiar now that i see it and makes the problem a little better.

thanks