Compute the coefficients [m, h, v] for f(x) = m * |x - h| + v from two control points: p1 (vertex) and p2 (a point on one arm).
Returns undefined if p1 and p2 share the same x-coordinate (slope undefined).
Compute the coefficients [m, h, v] for f(x) = m * |x - h| + v from two control points: p1 (vertex) and p2 (a point on one arm).
Returns undefined if p1 and p2 share the same x-coordinate (slope undefined).