# Thread: 360 degrees, not 390

1. ## 360 degrees, not 390

(pardon the first two posts--I wrote 390 degrees instead of 360)

Greetings. I need a geometry expert, please.

I have an 8 inch, 360 degree, 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?

Thanks very much
Dave Vanwerkhoven

2. ## Re: 360 degrees, not 390

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?

Code:
      |             *
|           *   * 8
|         *       *
|       *           *
|     *           *
|   *           *
| *           *
A o           *
| * 8     *
|   *   *
|     o C
|   *
| * 8
B o
|
We see that $\displaystyle \Delta ABC$ is an isosceles right triangle.
. . Hence: .$\displaystyle AB \,=\,8\sqrt{2}$

The ellipse has major axis $\displaystyle 8\sqrt{2}$ (vertical) and minor axis $\displaystyle 8$ (horizontal).
. . Hence: .$\displaystyle a = 4\sqrt{2},\;b = 4.$

The equation is: .$\displaystyle \dfrac{x^2}{16} + \frac{y^2}{32} \:=\:1$

3. ## Re: 360 degrees, not 390

Dear Dave Vanwerkhoven,
You need a heating contractor not a geometry expert.

4. ## Re: 360 degrees, not 390

Well i don't think you going to get good solution for this on this forum, i think you should take help from Engineer because he only give you the best solution. Geometry tutor any only help you out in geometry problems but in this case Engineer can help you better.