How do I get EU = k down instead of up?

Question

I have this:

\frac{\mathrm{d} B}{\mathrm{d} A}\bigg|_{}^{EU=k}

but with this my EU = k is above, but I want it below. How do I get it down?

Answer 1

Well, upon a request of Andrew Swann, I will make my comment an answer a bit fitter.

Certainly the question, the problem, is trivial and the solution requires only a little bit of attention:

\frac{\mathrm{d} B}{\mathrm{d} A}\bigg|_{}^{EU=k}

produces a derivative with a strange notation, to get the right form we need to erase {}^ from the expression before for put EU=k. Something almost obvious for anyone who knows the notation employed in LaTeX for superscripts (with circumflex) and subscripts (with underscore).

But another thing that strikes me, beyond the absence of any package for mathematics (such as amsmath or mathtool) that enhances the insertion of mathematical notation in our documents in addition to the tools of the mathematical environment; is the emphasis on writing math expressions in Roman and not italic letters as usual in LaTeX.

From the little I've read on the subject (most is from Javier Bezos in his book Typography and Scientific Notation) in Spanish of course, and from my own experience, I understand that the literal names in mathematics are composed in italics and not in Roman, and that they are used for the names of certain mathematical operators and functions, often with names of at leasts three letters, such as: div, sin, lim, etc.

It strikes me why the code in question, shows an effort to avoid the use of italics in the equation. I don't know if it's lack of experience or attention or for some particular reason. For me, a better way of expressing the equation in question is:

\frac{d B}{d A}\bigg|_{EU=k}

with amsmath:

\dfrac{d B}{d A}\bigg|_{EU=k}