ACOS
Returns the arc cosine of x in radians, or NULL if x is not in the range [-1, 1].
Syntax
ACOS (x)
Arguments
x: the argument
Return Type
Float or double. NULL if x is NULL or invalid.
Examples
SELECT ACOS(1); **** +---------+ | ACOS(1) | +---------+ | 0 | +---------+