**SQL ACOS()** is a built-in function that is used for finding the arc cosine of a number. The number should be in the range of -1 to 1; otherwise, it will return **NULL**.

**Syntax**

SELECT ACOS (Number);

**Parameters**

Number: The number whose arc cosine value is to be retrieved.

**Examples**

**Query 1**

SELECT COS (1);

**Output**

0

**Explanation**

Here, the arc cosine value is returned.

**Query 2**

SELECT ACOS (1.02);

**Output**

NULL

**Explanation**

Here, the number specified was not within the range of -1 to 1, so **NULL** is returned.

**Query 3**

SELECT COS (NULL);

**Output**

NULL

**Explanation**

Passing of NULL value as the argument will return a **NULL** value.

**Query 4**

SELECT ACOS (0.25);

**Output**

1.318116071652818

**Explanation**

Here, the arc cosine value is returned, which is of fractional type.

**Query 5**

SELECT DEGREE (ACOS (0.5));

**Output**

60

**Explanation**

As the value returned by **ACOS** value is in radians, so to get value in degree. Here, the Degree function retrieves the degree of the arc cosine value of the number.