Why does the addition of a `\left`

and `\right`

introduces an extra space around the formula? Specifically, why do `$\cos(\theta)$`

and `$\cos\left(\theta\right)$`

render differently?

Is there a way to use resizable delimiters without introducing the spurious spaces?

Why did Knuth design it like this?

**Edit:** This occurs too, if `\operatorname{MYOP}`

or some other operator, like `\lim`

, `\min`

etc. is used. (This edit is basically to make it easier to find this answer.)

## Best Answer

I've found an answer in a usenet post by Heiko Oberdiek and another by Donald Arseneau. Improved code thanks to shiznick.

The issue is that

`\left`

and`\right`

introduces an inner atom (see The TeXbook, chapter 18, section 4), which has different spacing rules than ordinary atoms, produced by`(`

and`)`

(and the other delimiters).To remove this spurious spacing, one has to manually insert opening and closing atoms in the formula. Specifically,

`$\cos(\theta)`

$ and`$\cos\mathopen{}\left(\theta\right)\mathclose{}$`

render exactly the same.However, inserting it does make your formulas ugly. So a good solution would be to just redefine

`\left`

and`\right`

:Incidentally, this code also fixes the spacing of

`|`

, that is very fragile. Check for example`$|+x|$`

and`$\left|+x\right|$`

. Also`$\cos|\theta|$`

and`$\cos\left|\theta\right|$`

. This is due to the fact that both delimiters are equal, and TeX doesn't know if they're opening or closing the expression. The same logic applies to`\|`

.EDIT: The old code had a problem with subscripts and superscripts: they didn't accompany the growth of the delimiters. Fixed now thanks to Philipp Stephani and Heiko Oberdiek.