# Getting \vphantom to work

1. Jan 17, 2017

### BvU

I found (nitpicking, I agree -- but that's what $\TeX$ does to you )$${dr\over dt} = {dr\over d\phi}{d\phi\over dt}$$ looking ugly and want to lift the two dr . However,

{dr\over dt} = {\vphantom {\phi} dr\over d\phi}{d\phi\over dt} didn't deliver as I expect:
$${\vphantom {\phi dr } dr\over dt} = {\vphantom {\phi} dr\over d\phi}{d\phi\over dt}$$ where omitting the \vphantom does take care of the lifting :
$${ dr\over dt} = {{\phi} \ dr\over d\phi}{d\phi\over dt}$$ (but I of course don't want the $\phi$)
anyone have a tip how to get this done ?

PS the ordinary \phantom does work as I expect -- vertically as well as horizontally:
$${\phantom {\phi } dr\over dt} = {\phantom {\phi} dr\over d\phi}{d\phi\over dt}$$

2. Jan 17, 2017

### Dr Transport

try \frac{}{} as opposed to \over

3. Jan 17, 2017

### BvU

Excellent ! Thanks doc !

\frac {\vphantom {\phi} dr} {dt} = \frac {\vphantom {\phi} dr} {d\phi} \frac {d\phi} {dt} does the trick

$$\frac {\vphantom {\phi} dr} {dt} = \frac {\vphantom {\phi} dr} {d\phi} \frac {d\phi} {dt}$$
and leaves me wondering why \over doesn't behave like that ...

4. Jan 17, 2017

### Dr Transport

why \vphantom?? shouldn't need it.

5. Jan 17, 2017

### BvU

Have to recant: also with \frac the d from $dr$ is sitting lower than the d from $d\phi$ which I find ugly.
Equally below the line: $dt$ is below $d\phi$

It's not much but annoying. See post #1.

6. Jan 17, 2017

### Staff: Mentor

Are you talking on screen? Then it must be a problem in MathJax. LaTeX renders the equation correctly without vphantom.

7. Jan 17, 2017

### Dr Transport

I agree, I just did both in TeXnicenter and they are identical in the pdf file......

8. Jan 17, 2017

### BvU

Yes, on screen. Both Chrome and IE11.
Haven't explored these other environments yet.

9. Jan 17, 2017

### Dr Transport

MathJax issue, not LaTeX issue.....

10. Jan 18, 2017

### BvU

I see your point: wrong forum
I'll have to get used to it -- an imperfect world

Last edited: Jan 19, 2017
11. Jan 19, 2017

### BvU

Have tried http://beta.mathjax.org/mathjax/latest/test/sample-dynamic-2.html -- doesn't show the problem I see on PF. No need to juggle with \vphantom indeed.
Is that link using MathJaX or is it faithful to $\LaTeX$ ?

Anyone know where to find a legible summary of MathJaX limitations ?

Could it be this isn't a MathJaX issue but a MathJaX implementation issue ? @jtbell, @Greg Bernhardt ?

\vphantom itself works alright: with \vphantom\int I can lift the d (more than I need for alignment with $d\phi$), but with \vphantom\phi it doesn't lift it enough to come to the same height as $d\phi$

12. Jan 19, 2017

### Staff: Mentor

Sorry, I'm not familiar with the detailed ins/outs of LaTeX and MathJax. I'm basically at the "Primer" level.

13. Jan 19, 2017