How it works ?
The following applet illustrates a hyperboloid of 2 sheets. The equation of this particular hyperbola is (x2 /a2)-(y2 /b2)- (z2 /b2)=1.
Note: This applet will only work if the blue point is on the sheet containing V_2.
V_1, V_2 = vertices
F_1, F_2 = foci