I would like to create an Excel spreadsheet with the appropriate
formulae to compute the distances between different points in
three-dimensional coordinates (X, Y and Z). So, for example, if I
decide Point A is at 15, 190, -5 and Point B is at 210, 185, 22, it
would be able to give me the distance between Point A and B
automatically. Obviously, I need to know how to enter all three
coordinates into the system for each point, and how to then
interrelate the points to one another on their graph.

I'm looking for relatively specific instructions, with the appropriate
functions and formulae listed to make this work properly in Excel.
Thanks!

Hi.
The basic formula is:
distance (Point3D x1 y1 z1) (Point3D x2 y2 z2)
    = sqrt ( (x1 - x2)^2 + (y1 - y2)^2  + (z1 - z2)^2 )

See the following web site for a full discussion under "coordinate
system":
http://fuzzyphoton.tripod.com/rtref_c.htm

There are any of a number of ways you can set this up in Excel, but
let's say that you put (x1, y1, z1) in spreadsheet cells A1, B1, C1,
and you put (x2, y2, z2) in cells D1, E1, F1.
Then in cell G1, you'd put your formula:
=SQRT((A1-D1)^2+(B1-E1)^2+(C1-F1)^2)

The distance would then display in G1. 


I hope this helps. Good luck.

The answer was quite good and quite complete, though the comments
below it really helped to flesh it out. In either case, I'm thrilled
this service exists. Take the money and accept my thanks!

There's a small (but huge) error in the above answer...

You have to take the absolute value of the differences between each
point to get the "distance" between them.  Otherwise, if any value in
the "second" point is greater than the corresponding value on the
"first" point, your results will be skewed.

formula should be:
=sqrt( abs(a1-d1)^2 + abs(b1-e1)^2 + abs(c1-f1)^2 )

Good sets of numbers to test on:
(0,0,0) and (3,4,12) .  Should result in 13 exactly.
(10,20,30) and (13,24,42) . Should get same answer.

Another good test:
(13,24,42) and (10,20,30) .  Should get same answer.

You should be able to switch the values for point 1 with point 2 and
get the same answer every time.  San Francisco is as far away from
Boston as Boston is from San Francisco.

Maybe I'm missing something, and I haven't taken in math class since
1989, but I fail to see why the absolute value is necessary. Doesn't
squaring a negative number only return a positive number???

Hi juggler,

Unless imaginary parts come to play, ABS(x1 - x2)^2 is exactly equal
to (x1 - x2)^2. Obviously you needed either a sleep or a mountain dew
at the time you wrote your comment :)

jmartin: do mean my comment or quesera's?

No need to take the absolute as the square of a negative number is
always positive. (Don't get lost in the long (incorrect) explanation
in the first comment...)

Ignore the chap who said there is a mistake in the answer concerning
negative distances. Squaring (A1-d1) etc does indeed allow for this in
the correct way.

Assuming that the X coordinates are in the 1st row (A1, B1, C1) and
the Y coordinates are in the 2nd row (A2, B2, C2) the actual Excel
formula should look like this  =SQRT(SUMXMY2(A1:C1,A2:C2)).

Please ignore the gibberish I posted above. The comment I meant to
post is:

Assuming that the coordinates for the first point are in the 1st row
(A1 , B1, C1) and the coordinates for the second point are in the 2nd
row (A2, B2, C2) the actual Excel formula should look like this 
=SQRT(SUMXMY2(A1:C1,A2:C2)). You can quickly add more sets of points
by highlighting all seven cells (the 3 for each point plus the one
cell that has the result in it) and then copy/pasting to a new set of
cells.

sorry, mea culpa magna.  sleep or mountain dew, definitely one or the
other.
you're all right and i'm wrong.

well, i'm wrong about the first answer being wrong, anyway.  my answer
is correct, but incompletely simplified.  that's what i get for doing
the math instead of looking it up.  :-)

apologies all around.

I would strongly suggest you to use StarCalc, instead Microsoft Excell.
StarOffice from Sun Microsystems has much more power than Microsoft's one.
StarOffice Homepage: http://wwws.sun.com/software/star/staroffice/6.0/index.html

Please ignore the gibberish I posted above. The comment I meant to
post is:

Assuming that the coordinates for the first point are in the 1st row
(A1 , B1, C1) and the coordinates for the second point are in the 2nd
row (A2, B2, C2) the actual Excel formula should look like this 
=SQRT(SUMXMY2(A1:C1,A2:C2)). You can quickly add more sets of points
by highlighting all seven cells (the 3 for each point plus the one
cell that has the result in it) and then copy/pasting to a new set of
cells.

Occasionally found your post about Mac X and Palm Desktop.

It's impossible to answer there, so have a look at link
http://www.palm.com/software/desktop/mac.html

it allows downloading for free 4.01 version of Pal Desktop for MAC, that
works on OS X.