Inserting an exponential formula

**SeanBorn** · 01-22-2013, 03:39 PM

Hi all!

I have an exponential formula that I have no Idea how to enter into a cell. The formula is;

y=2.8243*e to the power of 2E-0.5x

(I dont know how to type "to the power of" and get the type after it to be raised).

x is a given valuue of another cell and y is the cell that I am trying to calculate. I dont know what e and E are though.

Any help would be much appreciated.

Thanks.

**MrShorty** · 01-22-2013, 04:14 PM

I dont know what e and E are though.

e is the base for the natural logarithm. Most (if not all) programming languages/spreadsheets have a built in function for "e^x". In Excel, it is the =EXP() function http://office.microsoft.com/en-us/ex...in=HA102752955.

E is the way most computer languages handle scientific notation http://office.microsoft.com/en-us/ex...132.aspx?CTT=1

In the end, the function you gave would go into Excel as =2.8243*exp(2E-0.5*A1) if x is in A1.

**SeanBorn** · 01-22-2013, 04:28 PM

Thanks so much!

I am having trouble inputting it into the cell though. it doesnt like the E part and keeps trying to switch it to the cell "E2"

**shg** · 01-22-2013, 04:37 PM

In scientific notation, the exponent is always a whole number. You sure that shouldn't be something like

=2.8243*exp(2E-5*A1)

**SeanBorn** · 01-22-2013, 04:42 PM

Ah yes, thank you that worked.

I actually got that formula off a trend line i charted for a bunch of points. When displayed on the chart it puts a 0 in front of that 5. I figured if it had a 0 in front, so it must be a decimal, otherwise you dont need the 0... I just now zoomed in to see that there's no decimal point.

Thanks guys, this really helped a bunch.

**MrShorty** · 01-22-2013, 05:03 PM

Maybe I should not say anything, but, to anticipate the next question (why can't I calculate the right values from my trendline formula) are you certain that the 2E-5 coefficient for the x term is exactly 2.000000000E-5? It's a very common question, and frequently people find out that Excel chose to display to one significant figure, when the real value is 1.5287E-5 or 2.4825E-5 or something that, to one significant figure, displays as 2E-5. Format the trendline to apply a number format that will show you more significant figures to make sure you are copying the trendline correctly.