• May 9th 2012, 12:42 PM
Vanwerkhoven
Greetings. I need a geometry expert, please.

I have an 8 inch, 390 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
• May 10th 2012, 11:48 PM
daffodil1003
I don't understand question
__________________
• May 11th 2012, 07:35 AM
earboth
Quote:

Originally Posted by Vanwerkhoven
Greetings. I need a geometry expert, please.

I have an 8 inch, 390 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

1. Draw a sketch (see attachment)

2. I assume that the 8' are refferring to the diameter? The minor axis has then the length b = 4. The major axis has consequently the length

$\displaystyle a = \frac{4}{\cos(45^\circ)}=4 \cdot \sqrt{2}$

3. The equation of the ellipse is:

$\displaystyle \frac{x^2}{32} + \frac{y^2}{16} = 1$