Integrate problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg65493] Integrate problem*From*: "axman" <yuerlong at gmail.com>*Date*: Wed, 5 Apr 2006 06:55:37 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Hi, Group I am new to Mathematica and now meet one problem I can't solve by self. First I defined 3 functions: h, f and g \!\(\(h[t_] := \(-20\)*Cos[t] Exp[\(-t\)\/20];\)\[IndentingNewLine] \(f[x_, y_] := Cos[x] Sin[y];\)\[IndentingNewLine] \(g[Î±_, Î²_, t_] := If[t == 0, \(-1\), If[h[t] < Î², \(-1\), If[h[t] > Î±, \(+1\), g[Î±, Î², t - 0.1]]]];\)\) Now I try to integrate the function f[x,y]*g[x,y,10] on a triangle region: \!\(â?«\_\(-20\)\%20\(â?«\_\(-20\)\%x\((N[f[ x, y]\ g[x, y, 10]])\) \[DifferentialD]y \[DifferentialD]x\)\) The output result is strange. How to get correct answer for this integration? Thank you for help.