# Should you write \$a_1^2\$ or \${a_1}^2\$?

I apologize in advance if this is a duplicate, but I have looked and found no similar question.

We consider a \$n\$-tuple \$(a_1,\ldots,a_n)\$, and we want to square the first component \$a_1\$.

I read a long time ago that the correct way to do that is to write

``````{a_1}^2
``````

which transforms into

``````a_1^2
``````

which transforms into

But someone just told me that everybody writes

``````a_1^2
``````

so it is not a good idea to write otherwise, to avoid confusion with others.

Considering this, what would be the best way to write it according to you?

• in most math contexts, the "stacked" form is usual. but in disciplines like tensor analysis, an offset is required. so the "correct" way usually depends on the context. (actually, this is probably more a math question than a tex question.) – barbara beeton Mar 27 '18 at 13:08

From a mathematical view:

`{a_1}^2` seems to be the correct way, because the whole `a_1` getting raised to the power not just `a`.

But:

Could it have been done the other way?

Could we raise `a` to 2 and then "refer" to it's (alpha's family) first item?

No, we could not. (Not at the most of the cases of this symbol usage [See P.S.])

So, the better way is `a_1^2` because it is more comprehensive and doesn't bring things to a confusion.

P.S: If there is a need to make clear the way (or priority) of the usage (we always have the ability to declare what our symbolism means) we would probably had to use a parenthesis too to make it really clear: `(a_1)^2`