[Tex/LaTex] Displaying the binomial coefficient symbol in math mode


The problem is caused by the symbol of binomial coefficient (symbol of Newton), often used in math:


In my document I have formula:

$$ P(A) = \sum P(\{ (e_1,...,e_N) \})  =  {N}\choose{k} \cdot p^kq^{N-k}$$

which is rendered as:

enter image description here

but should be:

enter image description here

Best Answer

To fix this, simply add a pair of braces around the whole binomial coefficient, i.e.

{N\choose k}

(The braces around N and k are not needed.)

However, as you're using LaTeX, it is better to use \binom from amsmath, i.e.


Further, it is not recommended to use $$ ... $$, see Why is \[ … \] preferable to $$? Last, I'll note that amsmath provides different commands for 'continuation dots', including \dotsc for triple dots between commas.

 P(A) = \sum P(\{ (e_1,\dotsc,e_N) \})  =  \binom{N}{k} \cdot p^kq^{N-k}
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