Ok iam trying to get a spreadsheet developed for work ( use it for extra credit for post grad work at uni).

I have to get out r ^(2/3) (ie r to the 2/3rds power) out of an equation (eg reverse it out). Now i have the function of xroot of a number on my calculator but can't find the same function in excel. any ideas?

wes u developed some good spreadsheets, any ideas?

YOu need to talk to WES ... he is an Excell Guru ....

y = r ^ ( 2/3 )
y = exp(2/3* ln(r))

That might help if you can reverse that. The mathematica pages for roots are very pretty:

Square root:
http://mathworld.wolfram.com/SquareRoot.html 

Inverse functions:
http://mathworld.wolfram.com/InverseFunction.html 

Andrew

andrew thats what iam trying to reverse

the equation is (mannings equation)

Qy= (1/n) * (r^(2/3)) * (Se^(1/2))

I have Qy, n, Se but need to find r,

so r^2/3=Qy/(1/n)/Se^(1/2)

nor need to get rid of the 2/3 power to find r by itself


Iam sick of doing 3 pages of calcs to find the required channel size for a discharge point of a catchment then having to do it over again when when one of the planners wants to change the layout of the site!!!!
so developing a spread sheet to make it easier and mabye the scientist can use it to.

r^(2/3) = x
therefore
x = r^(3/2)

hth

Don't you mean

x = r^(2/3)
r = x^(3/2)

?

Andrew

^^^ What he said...
Yes, that's what i meant.

:thumb:thumb:thumb:thumb:thumb:thumb:thumb


thanks guys should have thought about the math way not the write formula for excel.

Hey LETS try n keep Excel simple...

I know how to do most things but lets keep it simple please

Now access is a different matter

I didn't reply to this yesterday as I was out riding my motorbike on a ride day for 10.5 hours. I'm a bit sore now.

Yes I could've helped, and yes I'm pretty familiar with Excel.