# LaTeX showing old images in preview

1. Nov 21, 2008

### Jonathan Scott

I've been trying to use LaTeX in a response, but the preview keeps showing images of different LaTeX expressions which I used in previous responses. This happens even for the most trivial case such as just a single letter X, both in ITEX and TEX tags. Is there something I need to do to reset it in some way?

2. Nov 21, 2008

### D H

Staff Emeritus
$$6 \,\frac{Gm}{c^2a(1-e^2)}$$

You will get an old image if your LaTeX code is invalid. For example, with [noparse]$$\frac {GmM{r^2}$$[/noparse]

I see $r^2$. You will see

$$\frac{GmM{r^2}$$

Edit:
Hmmm.

The "LaTeX image generation failed" is being shown for a valid LaTeX expression and the generated LaTeX image for the invalid expression is the image corresponding to the valid expresion. Weird.

3. Nov 21, 2008

### Redbelly98

Staff Emeritus
I will echo Jonathon's observation. It's frustrating when you're trying to give accurate information, and equations won't display properly. As a result I avoid using LaTex if at all possible. Luckily there are some https://www.physicsforums.com/blog.php?b=347" [Broken], but they're not as versatile as LaTex.

Last edited by a moderator: May 3, 2017
4. Nov 21, 2008

### Kurdt

Staff Emeritus
I think its a cache issue in the preview screen. This has been known about for a while. If you refresh each time you preview the problem should go away. Make sure you copy the contents of your post just in case something happens in the refresh.

5. Nov 21, 2008

### Redbelly98

Staff Emeritus
I'm pretty sure I tried a screen refresh the last time this happened to me (at least 2 weeks ago), and it didn't help. But enough time has passed that I'm not 100% sure. I'll try to remember trying this next time it happens.

6. Nov 23, 2008

### Ed Aboud

Whats the difference between TEX and ITEX anyway?

7. Nov 23, 2008

### Kurdt

Staff Emeritus
itex is inline latex so if you want an equation in a sentence it will not skew the lines of text.

8. Nov 23, 2008

### Ed Aboud

Oh right.

9. Nov 30, 2008

### Redbelly98

Staff Emeritus
I just made a post with Latex and found that:
• Refreshing in preview mode does not get rid of the old LaTex image
• Refreshing after actually posting does get rid of the old image and displays the correct one.

At least this is the case in Firefox, the browser that I use.

So this puts us in the somewhat awkward position of having to post, where others can view, before we are finished editing. I guess we can always put "WORK IN PROGRESS, DO NOT RESPOND (YET)" at the top of a post until it is really in its final form.

10. Nov 30, 2008

### Kurdt

Staff Emeritus
Oh well. That theory is shot down then.

11. Nov 30, 2008

### Redbelly98

Staff Emeritus
Not totally shot down. At least we have some way of seeing what should be there, even if it's not perfect.

12. Dec 1, 2008

### Fredrik

Staff Emeritus
I'm using Firefox too, and I don't have a problem with previews. Sometimes the wrong image shows up when I view what I just posted, but a refresh always takes care of that.

Edit: I got an old image in the preview today. I had already previewed the page and it looked fine except that I had written e(ipx) instead of e^{ipx}. So I changed it and previewed again. The old image was still there. Refresh didn't help. Then I noticed that I had actually written e^{ipx). So I replaced the ) with a } and previewed again. This time it looked the way I intended it to. No refresh needed.

Last edited: Dec 1, 2008