are the parameters used to chose one specific element of the family of functions.
For example, let's say we
want to implement a function that given the spring constant
</math> and the initial elongation <math> x_0 </math> of a spring, computes the time evolution of the elongation <math> x (t ; x_0, k) </math> by solving the Cauchy problem <math> x' = - k x\\ x(0) = x_0 </math>
==== Solution ====