Solved

# diagonal of irregular object

Posted on 2013-12-28
Medium Priority
418 Views
hy ,
have excel sheet that randomly calculates lengths of  8 sided object ,
i need to calculate diagonal of the object.
here is example

0
Question by:thmh
[X]
###### Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

• Help others & share knowledge
• Earn cash & points
• 5
• 3
• 3
• +2

LVL 84

Expert Comment

ID: 39743445
I can't resolve the shape of the object from that image, but if it is a box with rectangular sides, then the diagonal would be sqrt(length^2+width^2+height^2)
0

LVL 50

Expert Comment

ID: 39743453
It might help if you could post an image that shows the content in a bit more than a stamp size on a huge sheet. Use the snipping tool and resize the image to remove the white space. Then attach it.
0

LVL 84

Expert Comment

ID: 39743456
It may also help if you could indicate which lengths you know, and which diagonal you wish to calculate.
0

LVL 11

Expert Comment

ID: 39743546
gb = sqrt(hg^2)+(sqrt((ah^2)+(ab^2)))

That should do it...
0

Author Comment

ID: 39743826
ok , here is new picture ,
and Technodweeb can you explain your formula
0

LVL 11

Expert Comment

ID: 39743855
If all corners are 90 degrees then you can take the hypotenuse of the bah which is segment bh. Then take that length as part of the bhg to calculate the hypotenuse segment gb.

If the 8 corners are not 90 degrees, then I do not think my calculation will work as is.

By the way, the object you have drawn has only 6 sides and not 8 as you originally described. Are you wanting 6 sides or 8?

Then again this could be a big illusion for me...
0

LVL 84

Expert Comment

ID: 39743857
If bah and bhg are right angles, my previous answer holds.
If the object is irregular, more information would be needed to determine gb.
0

Author Comment

ID: 39744545
my mistake it's 6 sided irregular object , not 8 ,
there are all irregular triangles no 90 degrees corners and all lengths are known

so is there formula
0

LVL 84

Expert Comment

ID: 39744558
I still don't think that's enough information.
Even if the sides are known to be planar, which does not appear to be the case in your example,
then with lengths ab=bc=cd=da=be=ef=fc=fg=gh=he=dg=ah=1
you could end up with bg anywhere between 0 and 3 by changing the angles at each corner.
0

LVL 11

Assisted Solution

Gregory Miller earned 600 total points
ID: 39744710
Without some angle information, I am afraid the only way to solve would be to approximate. I cannot come up with any mathematical formula to define any of the corner angles which will be required to solve for the diagonal gb.
0

LVL 84

Accepted Solution

ozo earned 600 total points
ID: 39748382
There is not enough information to determine gb
The following sets of points have very different gb distances,
despite both satisfying the other specified lengths

a = (0.000000,0.000000,0.000000)
b = (12.000000,0.000000,0.000000)
c = (4.310529,2.207268,0.000000)
d = (7.500000,2.218751,6.231143)
e = (9.457264,4.313399,-4.891736)
f = (7.456191,0.706988,1.963153)
g = (12.000000,0.000000,0.000000)
h = (6.000000,8.533921,3.488867)

a = (0.000000,0.000000,0.000000)
b = (12.000000,0.000000,0.000000)
c = (6.791680,6.072348,0.000000)
d = (3.013889,7.662736,5.674413)
e = (5.097953,1.161319,0.114379)
f = (4.187521,9.108522,0.000000)
g = (0.932321,12.903739,0.000000)
h = (3.125778,6.259707,8.487967)
0

LVL 27

Assisted Solution

tliotta earned 400 total points
ID: 39750456
A frame can be constructed with tubes cut to the given lengths and connected with threads through the tubes tied at the corners. Having a physical model like that would demonstrate why it's not possible to calculate a diagonal with only the lengths of the edges known.

Such a frame is not rigid. It can be moved in all directions to cause the length of the diagonal to grow or shrink.

Now, once a solid interior exists, the diagonal becomes fixed. But the angles all become fixed at the same time. It's only when both the edges and the angles become fixed at the same time that the diagonal has a known length. The edges alone are not enough.

Tom
0

Author Closing Comment

ID: 39750970
so calculating diagonal is to complex or even impossible , will try another approach (question)
tnx
0

## Featured Post

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

How to get Spreadsheet Compare 2016 working with the 64 bit version of Office 2016
This article will show how Aten was able to supply easy management and control for Artear's video walls and wide range display configurations of their newsroom.
In this fifth video of the Xpdf series, we discuss and demonstrate the PDFdetach utility, which is able to list and, more importantly, extract attachments that are embedded in PDF files. It does this via a command line interface, making it suitable â€¦
Simple Linear Regression
###### Suggested Courses
Course of the Month12 days, 16 hours left to enroll