The standard inverse Trigonometric Arccosine function is supported, generating ACOS (expression) and returning a value of type float. When dragging an Arccosine operator into a variable, the following tree element is created.
Variable Creation > Input > Variables: SQL Elements pane - Trigonometric > Arccosine
Columns and/or other expressions can be moved into the (empty) branch of the tree. There are no special properties for the Arccosine operator.