Question: non-linear ode with procedures in it!

Hi,

I am trying to get hold of this DAE system

> Fx := proc (Sa, Fz) local DX, MUX, BCDX, CX, BX, EX, SHX, SVY, x, Y, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, FZ; FZ := Fz; b0 := 1.490000; b1 := (-1)*28.08998; b2 := (-1)*1401.6957; b3 := 101.33759; b4 := (-1)*172.59867; b5 := (-1)*0.61757933e-1; b6 := 0.15667623e-1; b7 := .18554619; b8 := 1.0000; b9 := 0.; b10 := 0.; DX := b1*FZ+b2*FZ; BCDX := (b3*FZ+b4*FZ)*exp(-b5*FZ); CX := b0; SHX := b9*FZ+b10; EX := b6*FZ+b7*FZ+b8; BX := BCDX/(CX*DX); SVY := 0; x := Sa+SHX; Y := DX*sin(CX*arctan(BX*x-EX(BX*x-arctan(BX*x))))+SVY; return Y end proc;
print(??); # input placeholder

> eq2 := y(t)-x(t) = 0; eq1 := diff(x(t), t)+Fx(x(t), y(t)) = 0; sys := eq1, eq2; ic := x(0) = 0, y(0) = 0;
print(??); # input placeholder
> sol = dsolve({ic, sys}, numeric);
%;
Error, (in dsolve/numeric/process_input) input system must be an ODE system, got independent variables {t, 0.3344992810e-1*exp(0.61757933e-1*y(t))*x(t)-arctan(0.3344992810e-1*exp(0.61757933e-1*y(t))*x(t))}
>
kindly help