To use the square root function in a column formula, simply raise your expression to the 0.5 power.
You can calculated the square root in the column formula calculator, but it is not a dedicated button. The square root is the number you can square to get to original number, and from algebra:
(x^(1/a))^a=x
so to get the square root you need to calculate x^(1/2)
See below:
