



 
Hi Bill, I think you are referring to Soren's question about the roof on an octagonal birdhouse. I used a similar method to approach your question. In my diagram $AB = 17.25, BE = 29.9375, DC = 6 \mbox{ and } CF = 12,$ all in inches. The distance from the edge $BE$ to the edge $CF$ is 20 inches which gave me a height of 16.5359 inches. This is the vertical distance from the base to the top. $n_1$ and $n_2$ are unit vectors that are perpendicular to the faces $ABCD$ and $BEFC.$ The angle between these vectors has the same measure as the angle between the faces $ABCD$ and $BEFC.$ I used Wolfram Alpha to do the calculations I needed. Below are the inputs and outputs.
Thus you should set the blade of your saw to 74.4428/2 degrees which is approximately 37.25 degrees. I hope this helps,  


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