Do you mean you want to find the slope of the curve at some point
Or do you want to display a tangent line on the chart?
Is your data generated from a formula or it just a list of numbers
I usually fit the date to a polynomial; I use LINEST to get the value of the
coefficients into cells.
Then I work out the coefficients of the differential dy/dx and then compute
the tangent / slope at some point
Doubtful anyone else is interested in this so why no send me private email
get my email address from my website
best wishes
