In MariaDB, ACOS() is a built-in numeric function that returns the arccosine (inverse cosine) of its argument.

In other words, it returns the value whose cosine is the argument.

Syntax

The syntax goes like this:

ACOS(X)

Where X is a valid expression that resolves to a number between -1 and 1.

Example

Here’s an example:

SELECT ACOS(0.32);

Result:

+--------------------+
| ACOS(0.32)         |
+--------------------+
| 1.2450668395002664 |
+--------------------+

Here are some more examples:

SELECT 
    ACOS(0),
    ACOS(-1),
    ACOS(1);

Result:

+--------------------+-------------------+---------+
| ACOS(0)            | ACOS(-1)          | ACOS(1) |
+--------------------+-------------------+---------+
| 1.5707963267948966 | 3.141592653589793 |       0 |
+--------------------+-------------------+---------+

Out of Range Argument

The argument must be between -1 and 1. If not, null is returned.

Example:

SELECT ACOS(2);

Result:

+---------+
| ACOS(2) |
+---------+
|    NULL |
+---------+

Missing Argument

Calling ACOS() without an argument results in an error:

SELECT ACOS();

Result:

ERROR 1582 (42000): Incorrect parameter count in the call to native function 'ACOS'