### Probability density function - multivariate random variable

Hi experts!

I know that many of you are professional mathematicians. My question is about statcistics and sage:

given two independient random variables `X`

and `Y`

(with a probability density function `fX`

and `fY`

), and the multivariable random variable `A`

defined by: `A=h(X,Y)`

,

How can I obtain the explicit equation of probability density function of random varible ~~A?~~`A`

?

I only know that the join probability density fuction `fXY`

is `fXY=fX*fY`

(because there are independent).

Like you can see in the article
http://en.wikipedia.org/wiki/Probability_density_function
section 'Multiple variables' we can write the pdf of `A`

using Dirac delta function.

Waiting for your answers.

Thans a lot!!