Let $r$ be the distance from the origin to a point $P$ with coordinates $x$ and $y.$ Designate the ratio $\frac{y}{r}$ by $s$ and the ratio $\frac{x}{r}$ by $c.$ Then the values of $s^2-c^2$ are limited to the numbers:
less than $-1$ and greater than $+1,$ both excluded
less than $-1$ and greater than $+1,$ both included