Symbolic Expansion

[ELSID]

Working with logarithms. I was wondering why the symbolic engine will not "expand" out the variables? Am I doing something wrong?

Also, I would like to work symbolically upfront. In the attached, I want to expand/combine/simplify in terms of log symbolically. I then want to set that result to a variable, L. This way I can "prove the math" before applying values to the variables. Problem that I have is that as soon as I assign "L" to the symbolics, it wants a value. If I modify, the symbolics, I have to "cut & paste" into a variable definition.

Hope the attached makes sense

This is in MathCAD 14 M030.

Is this fixed in version 15?

[RichardJ · Accepted solution]

Working with logarithms. I was wondering why the symbolic engine will not "expand" out the variables? Am I doing something wrong?

You are making a very common mistake. When doing algebraic manipulations people frequently make implicit assumptions about the domain of the variables, but Mathcad's symbolic engine (especially the MuPad engine in MC14 and later) does not.

Also, I would like to work symbolically upfront. In the attached, I want to expand/combine/simplify in terms of log symbolically. I then want to set that result to a variable, L. This way I can "prove the math" before applying values to the variables. Problem that I have is that as soon as I assign "L" to the symbolics, it wants a value. If I modify, the symbolics, I have to "cut & paste" into a variable definition.

Make L a functoin of the undefined valiables, just as you would in a purely numeric function defintion.

[ELSID]

As always, you have proven to me that I can totally be oblivious to the "simple" solution. Thanks

One more quirk. I can not figure out the error message. See bottom of sheet alpha is always between 0 and 1

NEVERMIND. Once it's a function, I needed to eliminate the "explicit" portion