Exponential Function Problem

B

Bernie Hunt

I've run into a problem I don't understand using power functions. I've only
done limited work with powers in Excel, but I've run into a problem with
this formula;

=(-0.01^ (2/3))

This returns #Num

I tried to reformat to
=POWER(-0.01, (2/3))

and still get the same #Num.

I split the exponent into
=((-0.01^ (2))^(1/3))
and this works.

Why don't the first two formats work?

Thanks,
Bernie
 
R

Ron Rosenfeld

I've run into a problem I don't understand using power functions. I've only
done limited work with powers in Excel, but I've run into a problem with
this formula;

=(-0.01^ (2/3))

This returns #Num

I tried to reformat to
=POWER(-0.01, (2/3))

and still get the same #Num.

I split the exponent into
=((-0.01^ (2))^(1/3))
and this works.

Why don't the first two formats work?

Thanks,
Bernie
Click to expand...

Look at HELP for operator precedence.

Unless instructed by the use of parentheses, Excel will evaluate the negation
operator prior to the exponentiation operator.

In your first two examples, you are trying to computing the exponent of a
negative number. My limited math background leads me to believe that the
example you give would result in an irrational number. But I'm sure others
more knowledgeable will chime in

In your last example, you are squaring the negative number first (which gives a
positive number) and then taking the root of that positive number.


--ron
 
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