# Sign error in Eulers formula in header on front page?

Edit: Turns out it's (maybe) not a sign error, but the vertical line in the plus might be hidden by the parenthesis in the background. It still appears like an error!

I noticed this today, on the site header (bottom right of the TeX-logo, both on meta and the main site):

Which I read to say

and it is wrong. The correct expression I believe to be $\cos(-y) + i \sin(-y)$ which simplifies to

My suggestion would be either to change exp(x-i y) to the more conventional

(or at least insert the minus sign in the right hand side).

• I have a few problems with my internet connection, so could be my side: the images don't work. – Johannes_B May 12 '18 at 14:59
• The images show up here, but the two last ones are TeX on transparent background, which makes them "invisible" on the link. – Andreas Storvik Strauman May 12 '18 at 15:09
• You are right but isn't there a + in the exponential? At least I see a dim vertical bar in the middle of the -. My interpretation is that this is (just) a rendering issue. – user121799 May 12 '18 at 15:13
• Hummm. If I stare at it long enough, the vertical bar appears. However if I look away and look back at it quickly it's gone again x') – Andreas Storvik Strauman May 12 '18 at 15:15
• But it definitely looks like a sign error when not zoomed in like crazy, and should still be fixed? – Andreas Storvik Strauman May 12 '18 at 15:16
• @AndreasStorvikStrauman In case this bothers you and you'd like to replace the image for yourself: tex.meta.stackexchange.com/a/7482/36296 – user36296 May 12 '18 at 15:53
• @samcarter I’m soo getting a duck! – Andreas Storvik Strauman May 12 '18 at 15:55
• @AndreasStorvikStrauman Just place the duck over the plus/minus sign and the problem is solved :) – user36296 May 12 '18 at 16:05
• @samcarter I think it is really time for a new package: duckmath ;-) This will make math the most popular subject in schools. ;-) And there would be a new sign: \semiplus. – user121799 May 12 '18 at 16:18
• So guys, completely off-topic: My machine refuses to find i.stack.imgur.com. Did anyone had this issue before? No images right here. – Johannes_B May 13 '18 at 8:46
• What OS do you have? – Andreas Storvik Strauman May 13 '18 at 8:47
• @AndreasStorvikStrauman The problem disappeared. No idea what was going on. – Johannes_B May 14 '18 at 5:28
• – Werner May 14 '18 at 17:23
• I think there is no vertical bar. It is something behind it that overlaps which is containing a \rangle, but if I tilt my screen the difference in opacity is clearly visible. I think you're right! – Skillmon May 17 '18 at 18:26
• @Johannes_B the leading i suggests that your link is imaginary. – Skillmon May 17 '18 at 18:28

## 2 Answers

I'm not sure... Seriously, I'm not sure. Below is an aggressive filtering. I think it could be just anti-aliasing (hinting) fail.

• related image: tex.meta.stackexchange.com/a/648/36296 – user36296 May 17 '18 at 8:24
• I agree with this! It's there maybe. If you look at it long enough, you can see it, but if you look away and right back at it, it disappears. It's an illution! Or as @marmot suggested, a \semiplus. – Andreas Storvik Strauman May 17 '18 at 11:23
• @samcarter Yes, in the link you share one can clearly see it is a real plus, not just a \semiplus ;-) – user121799 May 17 '18 at 13:58
• BUT: can it be fixed by some awesome person? <3 – Andreas Storvik Strauman May 17 '18 at 18:37
• @Andreas I afraid that even if we insisted it's a bug, it's too minor to be fixed, given the overall graphic design backlog of SE sites (AFAIK, there're still sites waiting for their design to be made). – yo' May 17 '18 at 21:04

TeX is not limited to typesetting correct maths beautifully.

It is equally capable of typesetting incorrect maths beautifully.

Hence, even if the equation is actually incorrect, it still reflects the purpose of the site as well as if it was correct.

If the equation appeared incorrect on maths SE or if the equation here looked ugly, whether correct or not, that would be quite a different kettle of porridge.

But it doesn't and it isn't, so it's not.

• Incorrect maths is ugly! – Andreas Storvik Strauman May 22 '18 at 6:34
• Then why not use Eulers identity which is scientifically proven to be the most beautiful equation in the world? – Andreas Storvik Strauman May 22 '18 at 6:38
• @AndreasStorvikStrauman No it isn't! Maybe you read the wrong maths. So 'most beautiful equation' = 'least ugly equation'? Anyway, where's the challenge in typesetting the most beautiful one? The challenge is to typeset the most ugly beautifully! – cfr May 23 '18 at 1:51
• First: see page 3 here. Also google most beautiful equation. Second: on the page it's not actually Eulers identity, but Eulers formula! They differ! – Andreas Storvik Strauman May 25 '18 at 0:54
• @AndreasStorvikStrauman Beauty is in the eye of the beholder. – cfr May 25 '18 at 1:47
• that’s not a very scientific approach now, is it? – Andreas Storvik Strauman May 27 '18 at 20:07
• @AndreasStorvikStrauman Why would you expect me to take a scientific approach? Why think a scientific approach to beauty is appropriate or even possible? – cfr May 27 '18 at 20:39
• I note that as many people down-voted as up-voted this. Presumably/possibly one down-voter has commented. What about the rest? (Just curious - this is Meta and the usual guidelines don't apply, so this isn't a gripe.) – cfr May 27 '18 at 20:40
• I wish there was another counter, though, which people could use to indicate whether they thought a post was serious or not. That would be of greater interest here than whether people agree or not. [Of course, the most beautiful maths is correct. It does not follow that all incorrect maths is ugly, that no incorrect maths is beautiful or that all correct maths is beautiful.] – cfr May 27 '18 at 20:42
• I don’t down vote posts like this just because I disagree. You have a valid point, and I actually upvoted your post :) – Andreas Storvik Strauman May 27 '18 at 21:11
• @AndreasStorvikStrauman On Meta, downvote just means disagree, I think. Anyway, I didn't particularly think you had - just that that would account for at most one of the down-votes. Thanks for the up-vote, though: negated one of the down-votes :-). – cfr May 27 '18 at 21:35
• We ducks are very good at mathematics, specially wrong mathematics. :) – Paulo Cereda Jun 5 '18 at 20:17