Excel Graphing, adding a smooth trend line

[ObiWanToby]

Does anyone know how to add a smooth trendline to this titration curve?

I've tried exponential and polynomial. Nothing seems to work. I want to try to get the equation of that line so I can take the second derrivitive and find where the slope goes off to infinity, which will give me my inflection point.

http://cid-c2d60dda0cfeed94.skydrive.live....on%20Curve.xlsx

[Lewism]

Right-click a point on your graph and select Add trend curve. You will have to choose the last one on the list. I have it in french and it says "Moyenne mobile". It should be something like "Mobile average".

*Edit*

Oops, you want to derrive that.

I guess Excel isn't powerful enough for that. It only support 6th degres polynoms :/

[ObiWanToby]

How does anyone actually use excel for anything then, what do chemists use?

[Lewism]

I guess it can be done with Matlab ou Maple or even R (if you are crazy :p like me)

But the problem when you have a high degree polynom, over 4th degree. It can become tricky to find the inflection point from the second derivative.

It did it for fun with R with level 15 polynom and and have:

y = 3.272812 -11.97394x +55.44856x^2 - 92.86500x^3 + 81.21282 x^4 - 42.40592 x^5 + 14.15273 x^6 - 3.124128 x^7 + 0.4604531 x^8 -0.04453005 x^9 + 0.002652193 x^10 - 0.00007.939329 x^11

And it become useless after that.