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View Full Version : Math Wizzez, I need your help...



ckinney
08-26-2009, 09:20 PM
I am working on getting my back yard together and would like to have a 12 foot octagon, can't remember how to calculate the length of each side, can anyone help me out on this one? or know a good web based calculator for this?

Thanks in advance - Chris

rynofan23
08-26-2009, 10:11 PM
I'll give this a try.

The angle from the center to a middle of one of the sides would be 22.5 (180/n). The radius of your octagon is 72", which would make this the adjacent side. What we need to figure out is the opposite side. Using a trigonometry function, we can find the opposite side by using 2 x radius x tan 22.5. This gives us 59.64675".

I'll let someone check my work. It's been a decade since I've done any trig.

Tai

By the way, I'm assuming 12' is going across.

ckinney
08-26-2009, 10:22 PM
I'll give this a try.

The angle from the center to a middle of one of the sides would be 22.5 (180/n). The radius of your octagon is 72", which would make this the adjacent side. What we need to figure out is the opposite side. Using a trigonometry function, we can find the opposite side by using 2 x radius x tan 22.5. This gives us 59.64675".

I'll let someone check my work. It's been a decade since I've done any trig.

Tai

By the way, I'm assuming 12' is going across.

Thanks - yes the 12' is going from one side to the other, not the points... if that changes anything...

rynofan23
08-26-2009, 10:43 PM
Thanks - yes the 12' is going from one side to the other, not the points... if that changes anything...

Nope, nothing changes. Here's my handy work if you care to see it. :p

http://i47.photobucket.com/albums/f159/cubsfanfromarkansas/bench/octagon.jpg

Tai

negreyjr
08-26-2009, 10:48 PM
Impressive! Very nicely done!

ckinney
08-26-2009, 11:08 PM
That is awesome, thank you so much.

I can now get started on another "honey-do"

Yet another reason why I absolutely love this site.

- Chris

TJCloutier
08-26-2009, 11:28 PM
Lol I can't believe you just attacked him matmatically :p I could never do that, I see no point in algebra.

rynofan23
08-26-2009, 11:36 PM
Lol I can't believe you just attacked him matmatically :p I could never do that, I see no point in algebra.

Actually, this proves that math can come in handy. How else was Chris going to attack his honey-do list? ;)

Tai

JamesNevans
08-27-2009, 12:02 AM
I knew it was really close to an even 5' but didn't want to do the math.

ckinney
08-27-2009, 12:10 AM
I knew it was really close to an even 5' but didn't want to do the math.

I was thinking the same thing, but couldn't find the calc to do it with, it has been ten years since I took a math class.

ragtop12
08-27-2009, 01:09 AM
Nix that... calc was in radians, not degrees. i second the above solution :)