## Taking the natural log of a negative number is Excel.

## Taking the natural log of a negative number is Excel.

(OP)

Is there a way to calculate the natural log of a negative number (It should yield two solutions) in Excel without getting an error message. Your help is greatly appreciated.

pmans

pmans

## RE: Taking the natural log of a negative number is Excel.

## RE: Taking the natural log of a negative number is Excel.

## RE: Taking the natural log of a negative number is Excel.

The IMLN(number) function works, but yields a "text" cell. Do you know how to change this into a "number" cell, so it can be used as part of an equation somewhere else in the spreadsheet.

Thanks in advance,

pmans

## RE: Taking the natural log of a negative number is Excel.

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Eng-tips forums: The best place on the web for engineering discussions.

## RE: Taking the natural log of a negative number is Excel.

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Eng-tips forums: The best place on the web for engineering discussions.

## RE: Taking the natural log of a negative number is Excel.

## RE: Taking the natural log of a negative number is Excel.

Doing complex math with the analysis toolpack is a pain in the a**. If you do a lot, get something like MathCAD.

## RE: Taking the natural log of a negative number is Excel.

Here is a follow-up question, related to the imaginary part of the solution. I've noticed that the imaginary part of the natural log of any negative number is 3.14..i or PIi. Do you guys know why that is? What's the significance of PI in the imaginary part of the solution?

Thanks in advance,

pmans

## RE: Taking the natural log of a negative number is Excel.

e^(i*Pi) = -1

from which it follows that

log(-1) = i*Pi

Then from basic (non-complex) maths we have

log[(-1)*(x)] = log(-1) + log(x)

QED

## RE: Taking the natural log of a negative number is Excel.

bml and jgrhist - it sounds like you are saying the only thing we can do with a complex result is parse it into real/imaginary and go from there - if so I disagree. excel has complex functions which work directly on complex numbers as posted from help below.

I apologize in advance if I have misunderstood your comments.

IMABS Returns the absolute value (modulus) of a complex number

IMAGINARY Returns the imaginary coefficient of a complex number

IMARGUMENT Returns the argument theta, an angle expressed in radians

IMCONJUGATE Returns the complex conjugate of a complex number

IMCOS Returns the cosine of a complex number

IMDIV Returns the quotient of two complex numbers

IMEXP Returns the exponential of a complex number

IMLN Returns the natural logarithm of a complex number

IMLOG10 Returns the base-10 logarithm of a complex number

IMLOG2 Returns the base-2 logarithm of a complex number

IMPOWER Returns a complex number raised to an integer power

IMPRODUCT Returns the product of two complex numbers

IMREAL Returns the real coefficient of a complex number

IMSIN Returns the sine of a complex number

IMSQRT Returns the square root of a complex number

IMSUB Returns the difference of two complex numbers

IMSUM Returns the sum of complex numbers

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## RE: Taking the natural log of a negative number is Excel.

Eng-tips forums: The best place on the web for engineering discussions.

## RE: Taking the natural log of a negative number is Excel.

IMREAL(IMLN(-15))=2.70805020110221

IMAGINARY(IMLN(-15))=3.14159265358979