ACOS
A mathematical function that returns the angle, in radians, whose cosine is the specified float expression; also called arccosine.
Syntax
ACOS ( float_expression )
Arguments
float_expression
Is an expression of the type float or of a type that can be implicitly converted to float, with a value from -1 through 1. Values outside this range return NULL and report a domain error.
Return types
float
Example
SELECT ACOS(-0.50e0);