Hello, Vanwerkhoven!

I have an 8-inch diameter chimney pipe coming into my basement at a 45 degree angle.

I need to cut out a tin heat shield that lays flat against the wall, around the pipe.

Obviously, it would be "eliptical-ish" (my word), but I wonder what the equation for this would be?

We see that is an isosceles right triangle.Code:| * | * * 8 | * * | * * | * * | * * | * * A o * | * 8 * | * * | o C | * | * 8 B o |

. . Hence: .

The ellipse has major axis (vertical) and minor axis (horizontal).

. . Hence: .

The equation is: .