# 2 quick notation questions re: vectors and transformations

1. Is it customary to omit one pair of parentheses and write $T \begin{pmatrix} 1\\2\\1\\1 \end{pmatrix}$ instead of $T \begin{pmatrix} \begin{pmatrix} 1\\2\\1\\1 \end{pmatrix} \end{pmatrix}$ to indicate the image of $\begin{pmatrix} 1\\2\\1\\1 \end{pmatrix}$ under T ?

2. When writing it out by hand, do you prefer the straight or curly underscore underneath "v" to indicate that v is a vector (as opposed to a scalar) ?

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As for your second question, I prefer not to use any special type of letter to indicate that something is a vector. Because then I have to think harder about the equations I'm looking at and the objects they involve. It may be a bit masochistic but I think it's helpful. – Weltschmerz Jul 17 '12 at 13:45

For (1), I would specify something like $v = \begin{pmatrix} 1\\2\\1\\1 \end{pmatrix}$, and then write $T(v)$. I think that omitting the parenthesis could be unambiguous, but writing $T \begin{pmatrix} \begin{pmatrix} 1\\2\\1\\1 \end{pmatrix} \end{pmatrix}$ frequently is going to get frustrating quickly.
I quite like the notation $\vec{x}$ for vectors in handwriting as well. – J. M. Jul 17 '12 at 14:01