'Double' FindRoot

*To*: mathgroup at smc.vnet.net*Subject*: [mg8690] 'Double' FindRoot*From*: Michaela Meier <michaela.j.meier at rz.ruhr-uni-bochum.de>*Date*: Mon, 15 Sep 1997 02:49:16 -0400*Organization*: Ruhr-Uni-Bochum*Sender*: owner-wri-mathgroup at wolfram.com

Hi, I've got another serious problem I'm trying to find a numerical solution to a set of three equations: 1) FindRoot[ {fa[0.1,x1]==fa[x2,x3], fb[0.1,x1]==fb[x2,x3], fc[0.1,x1]==fc[x2,x3]}, {x1,0.1},{x2,0.1},{x3,0.9}] Worst of all: fa, fb, and fc are defined as: (this is a simplified example !) 2) fa=Function[{y1,y2}, fr=FindRoot[ {a1 x + b1 y + c1 z == p1[y1,y2], a2 x + b2 y + c2 z == p2[y1,y2], a3 x + b3 y + c3 z == p3[y1,y2]}, {x,0.1},{y,0.1},{z,0.1}]; x + y + z /. fr ] Just typing 'fa[1,2]' produces NO error. But as soon as I start program 1) Mathematica says that it's expecting a 'list of length 3' Again: If I calculate 'fa' all by itself it returns a number for all combinations of y1 and y2 So what causes this error ?? Or isn't Mathematica able to do more than one FindRoot at the same time ???? Michaela