I have the function that I use to fit:

```
Double_t fun(Double_t *x, Double_t *par)
{
Double_t z2 = x[0] * x[0] / par[0] / par[0] + x[1] * x[1] / par[1] / par[1];
z2 *= par[2] * par[2];
return -sqrt(z2) + par[3];
}
...
TF2 *f = new TF2("f", fun, -50, 50, -50, 50, npar);
...
hist>Fit("f", "Q");
```

I want the process to be carried out on the condition that the `par[0]/par[1]`

relation is constant and equal, for example, 2. How to perform it?