# What is this letter?

1. Feb 2, 2012

### bobfei

Hi,

Could anyone tell me what letter the circled one is? I thought it might be “tau” τ or “gamma” γ, but none of the two looked exactly the same as it.

Bob

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2. Feb 2, 2012

### Nytik

I'm not sure, though it might help to know what the symbol is meant to represent... does it correspond to $\left|\vec{r}-\vec{r'}\right|$?

3. Feb 2, 2012

Looks like eta

4. Feb 2, 2012

### bobfei

Nytik,

Yes, exactly:
This symbol represent radius from a point electric source, and is found on page 235 of Griffiths, David J. - Introduction to Electrodynamics (3ed).

Looks alike, but I am not sure.

Bob

5. Feb 2, 2012

6. Feb 2, 2012

### bobfei

Borek,

It looks very close. I would agree with it.

Bob

7. Feb 2, 2012

### Nytik

That r looks like a perfect match! Now I'm wondering how Borek knew that typeface so well...

8. Feb 2, 2012

### Staff: Mentor

I didn't knew typeface, I knew the letter. That was just the best link with this kind of r I could find in a few minutes.

9. Feb 2, 2012

### _PJ_

10. Feb 2, 2012

### rollcast

http://en.wikipedia.org/wiki/Copperplate_script

That's the original style from which most "curly" scripts originated from.

11. Feb 2, 2012

### Staff: Mentor

I bet this kind of r is earlier than that and came from the cursive.