I have a plot of experimental data and I inserted an exponential trendline
that fits the data very well. I'd like to "differentiate" the curve as I need
its gradient at certain points; as in I need Excel to draw the tangent to the
trendline at a given point and tell me its equation. Can anyone help me do
this?

Thank you all so much.

I don't think Excel knows how to do this as a built in thing. Extract
the coefficients of the trendline to a worksheet (using a worksheet
function such as LOGEST or a utility that will extract trendline
coefficients to a worksheet). Then you can use the coefficients and
your knowledge of calculus to determine a formula for the slope of the
function at any point. Then use that formula to put together a series
of data points that you can plot as the tangent of the curve.


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MrShorty
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thanks loads, i'll try it out

"MrShorty" wrote:

>
> I don't think Excel knows how to do this as a built in thing. Extract
> the coefficients of the trendline to a worksheet (using a worksheet
> function such as LOGEST or a utility that will extract trendline
> coefficients to a worksheet). Then you can use the coefficients and
> your knowledge of calculus to determine a formula for the slope of the
> function at any point. Then use that formula to put together a series
> of data points that you can plot as the tangent of the curve.
>
>
> --
> MrShorty
> ------------------------------------------------------------------------
> MrShorty's Profile: http://www.excelforum.com/member.php...o&userid=22181
> View this thread: http://www.excelforum.com/showthread...hreadid=468456
>
>