# Correct way to typeset a bold and dotted math symbol?

OK, I've seen related questions which indicate that you only bold the main symbol and not subscripts, and a few other almost related questions. But what about when you are using a bold math symbol dotted?

That is, I have a letter which represents a vector. We've been writing vectors as bold letters, i.e \mathbf{u}.

We represent the first time derivative of this symbol by putting a dot on it. Should I bold the dot or not? That is choice:

1. \mathbf{\dot{u}}, or
2. \dot{\mathbf{u}}

Edit: All things equal, I prefer the way choice 2 looks.

• In a general setting, applying some formatting to a symbol (letter, or otherwise) changes its meaning. In a similar way that U is different from \mathcal{U}, say. So, I would keep the operator symbol (\dot in this case) the same and therefore not bold. – Werner Apr 29 '13 at 0:13
• I'd keep option 2. You are differentiating the vector, and thus there is no reason why the dot should be inside the "bolding" command. – Mario S. E. Apr 29 '13 at 0:18
• Ah the author forgot \dot inside the \mathbf... would be my reaction to that. – percusse Apr 29 '13 at 0:18
• @percusse huh? reaction to what? – Jeff Apr 29 '13 at 0:24
• Reading a bold dot. – percusse Apr 29 '13 at 0:27

No, you should not print the dot bold. It \dot means a derivative, why should one assume that it's bold version have the same meaning?
• @MarioS.E. It is difficult to give a meaning of (skalar) derivative of a vector, indeed. But if \matxbf{f}=(x^2,0,1) one can interprete its vector derivative as the scalar one. – Przemysław Scherwentke Apr 29 '13 at 0:25