# [PD] bouncing

marius schebella marius.schebella at gmail.com
Sat Oct 13 17:45:48 CEST 2007

```how would you call the angle/gradient that the equation has.
for example: f(x)=kx+b... if k=1, the line has a "gradient angle" of 45
degrees if k=2 the angle is ~63. angle=arctan(k).
marius.

Mathieu Bouchard wrote:
> On Sat, 13 Oct 2007, marius schebella wrote:
>
>> I haven't heard it before, but tried to translate it from german
>> (steigungswinkel)
>> any line that is defined by f(x)=ax+b and where a!=0
>
> That's called "linear" or "affine" equation.
>
> In one terminology, "linear" is the general case, and "linear
> homogeneous" when b=0.
>
> In another terminology, "affine" is the general case, and "linear" is
> when b=0.
>
> But that's probably not all that you want to support: you want also to
> support f(x)=b and the non-function case of a vertical line. The thing
> is, functions of 1 variable to 1 variable are all that they teach people
> in high-school, but if you want to compute things in which y and x are
> considered of equal importance and not hierarchised, you have to stop
> considering one as the function of the other. You could, for example,
> use plain equations (not functions) for things that don't move, and
> consider y,x to be functions of t for things that move.
>