Help me find a hypotenuse.

We should do math on here more often, this is entertaining, albiet slightly disheartening. Even the guy correcting the guy correcting the flawed proof, is incorrect. Angry was correct in his correcting, as acknowledged. No one should do math at 1:30 am.

But the answer to the question not asked, is lay it out on the floor where it goes. Buy the biggest coupling you'll use, space it off the walls half an inch, and that's where you drill your giant holes, for the pipe not the fittings. MAKE SURE TO CHECK FOR JOISTS, WIRES ETC.

This is purely cosmetic, right? Find a way to support sheetrock, whether it's wood straps or metal corner bead bent over or whatever. Stuff it full of batt insulation for sound deadening before you close it up. Double the sheetrock if you can for more.

llysgennad said:

We should do math on here more often, this is entertaining, albiet slightly disheartening. Even the guy correcting the guy correcting the flawed proof, is incorrect. Angry was correct in his correcting, as acknowledged. No one should do math at 1:30 am.

^this guy right here knows what's up.

In reply to AngryCorvair (Forum Supporter) :

High praise indeed. I'm honored 

To be fair, there has been a lot of correct math shown by several. But maybe the answer is not always the solution. Blasphemy, I know

If that line is 4.5 its one leg of an equilateral triangle.  You split the line tabled "9" in half so the other line is also 4.5

Applying the Pythagorean Theorem (square root of the some of squares) the line you call "X" has a length of (4.5^2 + 4.5^2)^.5  = 6.36.  (^ is the exponent sign)

I'm not clear what you are going to do with that answer though...  If the pipe is 4.5 inches O.D. then that plus material thickness is your minimum out to out wall thickness. 

llysgennad said:

We should do math on here more often

yes

OK, since I've been called out, can someone explain to me where my math was wrong?  (honest question)

My comment was this:

Nope.  x^2+x^2 definitely equals 9 if x^2 = 4.5. 

Help me out here please.  Where is the error?

You want to fit a 4.5" pipe inside a traingular enclosure.  I think I get it.

Let's do it this way.  You know that a 4.5" pipe would fit inside a 4.5" square box, but if you just use 4.5" for the sides of the triangle, the hypotenuse cuts right through the pipe.  The answer instead is something like this.

So, start with a 4.5" square box.  The diagonal across that box (hypotenuse) is basically 6-3/8"  Now you can subtract the distance from the corner of the box back to the tangent of the circle (roughly 15/16").  So now you take 6-3/8" minus 15/16" and you get just under 5.5" from the corner of the room to the outside of the pipe.

Since you're dealing with a 45/45/90 triangle, we now know that the other leg of both triangles is also the same (roughly) 5.5".  Double it to get your hypotenuse.  We could A+B=C again, but since we know they're the same, it just makes sense to skip that.

Dig the cheat picture below.

SVreX (Forum Supporter) said:

OK, since I've been called out, can someone explain to me where my math was wrong?  (honest question)

 

My comment was this:

Nope.  x^2+x^2 definitely equals 9 if x^2 = 4.5. 

Help me out here please.  Where is the error?

 

Your math is correct, but it won't fit the pipe.  If he makes a 9" hypotenuse, it will look like this.  You can't use the 4.5" radius as your leg because the circle doesn't fit in the corner.  You have to add for the distance from the corner to the pipe.

If we are counting square inches of material here to save money, it would take less drywall to make a square bump out to cover the pipe.  It would also look more like it belongs there.

I would throw the pipe in there and build to whatever I ended up with.  I have a friend that is an engineer that tries to plan too far ahead and usually ends up spending more time and money finding the hard way to do things.

In reply to Curtis73 (Forum Supporter) :

I'm very aware the formulas didn't fit the situation, but it was suggested my math was wrong. 
 

I posted the correct formulas on the previous page. 

In reply to Curtis73 (Forum Supporter) :

Correct. 
 

Those are the same things I posted on the first page with diagrams. 

Well crap. What happened to my post on page 1?

In reply to SVreX (Forum Supporter) :

Not a big thing, just missed a square. x^2 + x^2 = y^2 = 81, and leads to y=9, which you correctly stated. In your selected equation above, x^2=4.5, 

4.5 + 4.5 = 9 is correct by itself, but thats means y^2=9, which leads to y=3.

Jumping between triangles confuses the math. So, maybe right answer, bad explanation? I can elaborate after I make dinner for the family.

I know this a bad explanation. I like your abcABC triangle better

In reply to llysgennad :

Unfortunately my abcABC triangle seems to have disappeared. 

In reply to llysgennad :

I think you misunderstood my comment on that initial formula.  I left out a couple parentheses...

If (x^2) = 4.5

Then (x^2) + (x^2) = 9
 

Not 81. 
 

And x= 2.1213. And it is a completely meaningless formula for figuring out this problem. 
 

My abcABC triangles were better. 

SVreX

Without your post, this is hard to recreate. It all goes back to mtn's proof, and AngryCorvair's comment that it didn't match the picture, and that's where you said "NOPE etc..."

Taken in isolation, your equation is correct, but in the context of the now lost post, and the diagram it referenced, it was not.

So, using the p-theorem, if x= 2.1213, then y=3.

But using that or similar diagrams, multiple people including yourself came up with y=9, hence y^2=81. Working backward, x^2 +x^2=y^2=81. Solving that, x=6.364. But that was actually the hypotenuse of the smaller triangle, labeled x on the proof, where the bisect = 4.5. Circular reference complete.

So in summary, you can't have it both ways. Either y=9, or y=3, you can't have it both ways.

This is a really hard way to get to Dork status

My brain hurts

In reply to llysgennad :

Thanks. 
 

I don't know what happened, but I'm not gonna recreate that post. Yes, I know how to do the math. But pizza boxes are much more effective. 

In reply to SVreX (Forum Supporter) :

And to get to the amount of beer boxes it would take I would probably be best advised to not be messing around with plumbing.

QuasiMofo (John Brown) said:

In reply to SVreX (Forum Supporter) :

And to get to the amount of beer boxes it would take I would probably be best advised to not be messing around with plumbing or MATH!

Fixed it for you!

I just have to say that I my Calc teacher in HS told us that we'd never use any of this crap in real life, but the point to teaching math is like weight lifting or jogging.  It forms complex synapse relations that enhance our critical thinking ability.  My uncle was a lifetime mechanical engineer for 3M, and even he (as he tutored me in Calc) said that he never uses it much.

Now, here I am as a theater technical director constantly using algebra, trig, and light calculus to do maths.  I don't remember much of the complex stuff, but I can't escape the fact that I think the math workout my brain got as a kid really helps me logic through things better than most.  Stuff just clicks with me.  Thanks Mr. Walker.

SVreX (Forum Supporter) said:

In reply to llysgennad :

Thanks. 
 

I don't know what happened, but I'm not gonna recreate that post. Yes, I know how to do the math. But pizza boxes are much more effective. 

I'm absolutely sure you do, no question. And pizza is always the answer I'm looking for!

When it comes to this kind of math, Paul probably puts us all to shame.

Laughing over here because you're all assuming that the corner in the house is actually a right angle.

I'm a car guy, not a construction guy and I know houses are almost never square.