fitting to a integral function

I have x and y data and im trying to fit to an integral equation and obtain the parameters x(1), x(2), and x(3)

This is the fitting equation

(1-(6*x(1))/(pi*sqrt(x(2))))*int(((((x(3)*cos(x(3))-sin(x(3)))^2)*exp(-1*fittingx))/((x(3)^2)*((sin(x(3)))^2)+x(2)*((x(1)/x(2))*(x(3)*cos(x(3))-sin(x(3)))+sin(x(3)))^2))

The integral is from 0 to infinity d(x(3))

Thanks!

[darova]

What about fit or lsqcurvefit?