# Tag Info

One example that comes to mind is modelling the position of a diver (or of a diver's head). Let $t$ be the time elapsed since jump. Let $d(t)$ be the diver's distance from the water and define $d(t)>0$ to be "above water" and $d(t)<0$ to be below water. (It should be obvious why $d(t)=0$ represents being "at the surface"). If we use a quadratic model, ...