Excel exponents

[Hobart]

My version of Excel 97 will solve =exp((5/8)^2) but it will NOT solve
=exp((5/8)^2.2). Whenever I put any decimal fraction for an exponent in
=exp( ) it will not solve it. I get #NUM!. My TI83+ will solve it.
Thanks

 

[JE McGimpsey]

My version of Excel 97 will solve =exp((5/8)^2) but it will NOT solve
=exp((5/8)^2.2). Whenever I put any decimal fraction for an exponent in
=exp( ) it will not solve it. I get #NUM!. My TI83+ will solve it.
Thanks

While this is a MacXL newsgroup, all versions of XL should be able to
calculate =EXP((5/8)^2.2).

What happens if you put

A1: =5/8
B1: =2.2
C1: =EXP(A1^B1)

???

 

[Hobart]

While this is a MacXL newsgroup, all versions of XL should be able to
calculate =EXP((5/8)^2.2).

What happens if you put

A1: =5/8
B1: =2.2
C1: =EXP(A1^B1)

???

 

[Hobart]

 

[CyberTaz]

I just copied your formula : =exp((5/8)^2.2)

And pasted it into a cell with an immediate result on pressing return of:

1.427006575

Using Excel 2004... Also tried a few others with no problem.

I don't know if this is the correct result, but it definitely didn't produce
an error. Is there a possibility that there's some sort of gremlin lurking
in the workbook, or is this happening in more than one file? Might any of
your Options settings be having an impact?

You might try : microsoft.public.excel.worksheet.functions to see if there
is anyone more familiar with 97.

Regards |:>)
Bob Jones
[MVP] Office:Mac

 

[JE McGimpsey]

[/QUOTE]

How bizarre!

Do you get the same error when you try

=EXP(0.355578945903531)

(since (5/8)^2.2 = 0.355578945903531)?

How about:

=EXP(1)^((5/8)^2.2)

????

 

[Hobart]

How bizarre!

Do you get the same error when you try

=EXP(0.355578945903531)

(since (5/8)^2.2 = 0.355578945903531)?

How about:

=EXP(1)^((5/8)^2.2)

????
OK, Thanks. I left out an important sign in my initial post. Sorry. It should have read =exp((-5/8)^2.2). All your suggestions work for a POSITIVE ratio, but none works for a negative ratio. The answer my TI83 gives me is 0.70077. Excel still does not work regardless which suggestion I use. Thanks.[/QUOTE]

 

[JE McGimpsey]

I left out an important sign in my initial post. Sorry. It should
have read =exp((-5/8)^2.2). All your suggestions work for a POSITIVE
ratio, but none works for a negative ratio. The answer my TI83 gives
me is 0.70077. Excel still does not work regardless which suggestion
I use.

Ah, now that's a whole different kettle of fish.

First, it has nothing to do with EXP(). Try

=(-5/8)^2.2

and you'll get the #NUM! error as well.

That's because the general solution for non-integral roots of negative
numbers requires the use of the complex number space rather than the
real number space. I'm not sure which method XL uses for the
exponentiation operator (^), but the two most common are the logarithm
method and the rational exponent method.

The logarithm method can't be used to return a real number when the base
is negative, because the inverse log (e^x) is positive for all real
exponents.

The rational exponent method can't be used since f(b) = b^x is not
continuous when b<0 and x is real.

There are special cases that produce real numbers: (a) when x is
integral, and (b) when x is of the form m/n, with n an odd number. Your
case falls in category (b) since 2.2 = 11/5, but you have to do some
manipulation to get XL to calculate it:

=((-5/8)^(1/5))^11

 

[Hobart]

Ah, now that's a whole different kettle of fish.

First, it has nothing to do with EXP(). Try

=(-5/8)^2.2

and you'll get the #NUM! error as well.

That's because the general solution for non-integral roots of negative
numbers requires the use of the complex number space rather than the
real number space. I'm not sure which method XL uses for the
exponentiation operator (^), but the two most common are the logarithm
method and the rational exponent method.

The logarithm method can't be used to return a real number when the base
is negative, because the inverse log (e^x) is positive for all real
exponents.

The rational exponent method can't be used since f(b) = b^x is not
continuous when b<0 and x is real.

There are special cases that produce real numbers: (a) when x is
integral, and (b) when x is of the form m/n, with n an odd number. Your
case falls in category (b) since 2.2 = 11/5, but you have to do some
manipulation to get XL to calculate it:

=((-5/8)^(1/5))^11

Thanks, I appreciate your answer. That should do it!