a problem with integrate

*To*: mathgroup at smc.vnet.net*Subject*: [mg72669] a problem with integrate*From*: "starryin" <starryin at gmail.com>*Date*: Sun, 14 Jan 2007 05:02:52 -0500 (EST)

hello everyone,i'm a student in China.i meet with a problem when i using mathematica to do this expression ¦Ò[x0_, y0_, y1_, z1_] := N[(1/10)*Sqrt[x0^2 + (y1 - y0)^2 + z1^2]*(Abs[y1 - y0]/x0 + 1)] f[y_, z_, y1_, z1_, x0_, y0_] := N[1/((2*Pi*¦Ò[x0, y0, y1, z1]^2)*N[e^(((y - y1)^2 + (z - z1)^2)/(2*¦Ò[x0, y0, y1, z1]^2))]),5] D1[x0_, y0_] := NIntegrate[f[y, z, y1, z1, x0, y0], {z1, 0, 2.44}, {y1, 0, 69}, {z, 0, 2.44}, {y, 30.84, 34.5}] after i define the function ,i input D1[3,5] to get one answer ,but i got a warning message: Integrand epr(i can not paste the expression here) is not numerical at {z1, y1, z, y}= {1.22`, 34.5`, 1.22`, 32.67'}. who can tell me how can i solve the problem? do i need to use Integrate instead of NIntegrate? or do i need to add some other parameter ? i' m so sorry that my english is not good enough to express my question ?but i still wish some one can solve my problem thanks!