### Begining data
We will use next coefficients

{{{
a=input(1.2); b=input(0.9); c=input(1.0); p=input(1.3)
}}}
### Elliptic paraboloid

{{{
<< (x^2)/(a^2) + (y^2)/(b^2) = 2*p*z
z_elp = ((x^2)/(a^2) + (y^2)/(b^2))/(2*p)
chart3d({x: x, y: y, z: z_elp, color: "blue", width: "250", xaxis: "auto", yaxis: "auto"})
}}}
### Hyperboloid of one sheet (half)

{{{
<< (x^2)/(a^2) + (y^2)/(b^2) - (z^2)/(c^2) = 1
}}}


{{{
z_h = \(((x^2)/(a^2) + (y^2)/(b^2) -1)*c^2)
chart3d({x: x, y: y, z: z_h, color: "red", width: "250", xaxis: "auto", yaxis: "auto"})
}}}

### Hyperbolic paraboloid
{{{
<< (x^2)/(a^2) + (y^2)/(b^2) + (z^2)/(c^2) = 1
}}}


{{{
z_hp = ((x^2)/(a^2) - (y^2)/(b^2))/(2*p)
chart3d({x: x, y: y, z: z_hp, color: "brown", width: "250", xaxis: "auto", yaxis: "auto"})
}}}