When the ratios of the values of a variable y to the corresponding values of another variable x all equal
a constant k, y is said to be proportional to x, and the constant k is called the constant of proportionality.
Because =k, you can solve for y to get y = kx. In the case of the arcs that are intercepted by a
225° angle, is the arc length s proportional to the radius r? If so, what is the constant of proportionality,
and what equation gives s in terms of r?