1. May 17, 2013

### Nikitin

Have you ever struggle to do a simple math/physics problem correctly for a long time JUST because of a ridiculous oversight you repeatedly made?

Last edited by a moderator: May 17, 2013
2. May 17, 2013

### WannabeNewton

Haha in fact yes. When I was learning topology there was a problem at the end of the chapter on connectedness and compactness which asked to show that if $X$ is a topological space and $CX = (X \times I)/(X \times \{0\})$ is the cone on $X$ then $CX$ is locally connected iff X is connected and locally path connected iff X is locally path connected. I was wracking my head over the problem for days on end and it was driving me quite insane but eventually,thanks to micromass, the solution was found and it turned out to be embarrassingly trivial because I had completely forgotten about fibers and saturated subsets associated with quotient maps, which in retrospect is shameful because they are very important when dealing with properties of quotient spaces.

Another time, I was trying to show that Maxwell's equations in curved space-time implied local charge conservation $\nabla^{a}j_{a} = 0$ but for some reason I kept running into dead ends. It turned out I kept on making the mistake of saying 2 - 2 = 4 lmfao

3. May 17, 2013

### reenmachine

I lost count of how many times I did it on this very site in the last 2 months :rofl:

4. May 17, 2013

### MarneMath

I make that error a lot. If i'm in a hurry, I will often go "ok so 2 + 2 = 4" in my head but when i'm writing it down, i'll write 4 + 2 = 6. So when I review my work, I don't see an error because of course 4 + 2 = 6 -_-.

5. May 17, 2013

### WannabeNewton

It's funny how the little mistakes are the ones that screw you over xP I blame the media!

6. May 17, 2013

### Staff: Mentor

Once during a derivation in a lecture, I set up an integral on the board, then proceeded to take the derivative. A few steps later, one of the students finally got around to correcting me.

7. May 17, 2013

### jobyts

8. May 17, 2013

### hotvette

Once, in a graduate level partial differential equations class in a large lecture hall, I spaced for a second and missed a step of a derivation. When I interrupted the professor (via microphone) to ask how he'd done the previous step, he replied with a snide comment about me not knowing how to solve two equations with two unknowns. For the next several weeks I was chided by other students about the incident. People can be rather mean. Of course, I never opened my mouth during class the rest of the semester.

9. May 17, 2013

### Staff: Mentor

I did many mistakes, but the one I remember was made by a friend of mine back in seventies - after solving some kind of a problem correctly he tried to rearrange the final answer and he canceled $\frac 2 2 = 0$. It became proverbial in our group.

10. May 17, 2013

### Staff: Mentor

I hope that's really your daughter because that's so cute.

11. May 17, 2013

### trollcast

From last nights revision

$\displaystyle x + x = x^2$

and

$\displaystyle e^0 = 0$

Although theres probably been worse than that before.

12. May 17, 2013

### SW VandeCarr

You didn't really do that, did you?

13. May 17, 2013

### SW VandeCarr

$e^{i\pi}-1=0$

14. May 17, 2013

### trollcast

Well not like that but in the middle of a solution I wrote both of those down and then wondered why my answer didn't match the mark scheme

15. May 17, 2013

### AlephZero

Back in the days when debugging computer programs meant doing hexadecimal mental arithmetic, I sometimes got brain-fade with ordinary decimal arithmetic - e.g. mistakes like 5 times 4 = 32 (because 32 = 0x20).

16. May 17, 2013

### collinsmark

I think the second one is a pretty common mistake. I haven't done that one in awhile, but I have done it before. For example, consider:
$$\int_0^a e^x \ dx.$$
Many students would mistakenly evaluate that to be
$$\int_0^a e^x \ dx = e^a,$$
which of course is not correct.

17. May 17, 2013

### phosgene

This happens to me so often that it's not funny (or is it?). I tend to do long stretches of study which sometimes make me feel like a zombie. I think my worst one was accidentally doing commas instead of plus signs when calculating a dot product. In my defense, the next step was correct as I'd continued on assuming that I'd written '+'s...

18. May 17, 2013

### Julio R

I'm only in High School, but I make simple arithmetic mistakes all the time.

19. May 17, 2013

### mathwonk

This is sort of mathematical - I once complained to a grocery store clerk that all the yogurt was outdated, because I forgot what month it really was. He got a kick out of that. I always try to avoid him since then.

I've got it. Once I asked a question of a Fields medalist about his specialty and he began to write briefly on a piece of paper, then stopped without a word. Since I could not see where he was going with it, I thought he was stumped and said "That's ok, I didn't really need it." When he looked at me oddly, but still without a word, I asked if I could have the paper. An hour later in my office, after he had gone home, I realized that what he wrote had completely solved my problem. It took me 20 years to mention it again and thank him.

Last edited: May 17, 2013
20. May 17, 2013

### Julio R

Did the clerk know you have a degree in math? That would make it more embarrassing.