Put trace on and move x to create hyperbola. Refresh the screen and then move the foci apart and recreate a new hyperbola.
Turn off trace. Turn off segments [i]p[/i] and [i]q[/i] the ones showing the distances. Turn on conic "[i]c[/i]" the hyperbola last constructed. Turn on point M--the center, and points [i]V1 [/i]and [i]V2[/i], the vertices. Turn on lines [i]m[/i] and [i]n[/i]--the asymptotes. Now move the foci around and see what happens.