/sci/ - Science & Math

Based.

>>11282925
I'll try to explain it more explicitly.
We have [math]V(h, r)[/math], the volume is a function of the radius and the height. Since [math]r(h)[/math], we can also give the volume as exclusively a function of the height,, [math]V(h(r), r)=V(r)[/math].
So if we let r change by [math]\delta r[/math], then we can compute either [math]V(r+ \delta r)[/math] or [math]V(h, r + \delta r)[/math].
These are two different things, and knowing when to use which depends on context, so you'll figure it out with practice.