Hi,

I have the following problem: I have a function to evaluate the obliquity of the ecliptic (astronomy) in the form:

Code:

`f(t) = a + bt + ct^2 + dt^3`

Its derivative (rate) is:

Code:

`derivative of f(t) = b + 2ct + 3dt^2`

Everything works out until here. But I've improved the formula; but now the t factor is equal to t/100;let's call it t', and with the new coefficients a', b', c' and d':

Code:

`f_2(t') = a' + b't' + c't'^2 + d't'^3`

If I calculate f_2 for a given t the result is the same, but improved. But what about the derivative of f_2? It's:

Code:

`derivative of f_2(t') = b' + 2c't' + 3d't'^2`

The rate, or derivative is referred to t' = t / 100; to referrer it to t, must I divide de derivative of f_2 by 100?

Kind regards,

Kepler