## Fitting a polynomial code

on 19 Sep 2013

### Walter Roberson (view profile)

I have to fit a polynomial

F(t)= 2F[e^(t/tr1) + e^ (-t/tr2)]^-1

where I have to find parameters tr1 and tr2

## Products

No products are associated with this question.

### Walter Roberson (view profile)

on 19 Sep 2013

That is not a polynomial. Polynomials only have their variables as basic terms with non-negative integer powers. If you have e^x where x is one of the variables then the expression is never a polynomial.

You appear to have F on both the left and right. Is that intended to be a recursive definition? If so then is the expression

```F(t) = 2 * 1 / F(exp(t/tr1) + exp(-t/tr2))
```

or is it

```F(t) = 2 * F[1 / (exp(t/tr1) + exp(-t/tr2)))
```

Either one is going to be non-trivial to find the expanded form, and there is a good chance that both tr1 and tr2 found would be complex.

#### Join the 15-year community celebration.

Play games and win prizes!

MATLAB and Simulink resources for Arduino, LEGO, and Raspberry Pi