The most likely cause is that you are working with two few digits. If you
format the trendline equation to display more digits I am sure you will find
all is well,
Of course, this problem of copying values from the equation is fraught with
problems - typos resulting from arthritic fingers or from poor reading
glasses being some of them
Best to use LINEST to get the coefficients into cells; see
http://www.stfx.ca/people/bliengme/E...Polynomial.htm

best wishes
--
Bernard V Liengme
www.stfx.ca/people/bliengme
remove caps from email

"E0sysengiineer" wrote in message
...
I fitted some data using the trend line tool. The fit purportedly was a
3-rd
order polynmial. When I create a column of values using the coefficients
that Excel found (Display equation), I find the data does not overlay the
trend line. I created data in the range of the fit so there is no error
due
to extrapolation and the fit R value was 0.9999. Is there an error in the
routine that reports the coefficients for polynomial fits? If so, is the
re
a patch or work around?

Thanks