When a probability measure m on a topological vector space E is well-a
dmissible in a direction k is-an-element-of E, the conditional law in
the direction k given the other directions is absolutely continuous wi
th respect to the Lebesgue measure. We shall prove that its density fu
nction is differentiable (in the sense precised below) and we shall ca
lculate their derivatives. We give then two applications of such calcu
lations.