? ACOS() Function in SQL

The ACOS() function returns the arc cosine (inverse cosine) of a number — the angle (in radians) whose cosine is the specified number.

? Syntax

SELECT ACOS(number);

• Input Range: -1 to 1

• Output: Value in radians between 0 and ? (approximately 3.14159)

? Basic Example

SELECT ACOS(1) AS result;-- Output: 0.00000 (cos?¹(1) = 0 radians)SELECT ACOS(0) AS result;-- Output: 1.5707963 (cos?¹(0) = ?/2 radians)

? With a Table Example

Assume a table angles:

Query:

SELECT id, value, ACOS(value) AS angle_in_radiansFROM angles;

? Use Cases

• Trigonometric calculations (especially in geometry, physics, or geolocation)

• Great-circle distance (e.g., in Haversine formula for calculating distance between two lat/long points)

? Supported In

• ? MySQL

• ? PostgreSQL

• ? SQL Server (from SQL Server 2012+)

• ? Oracle

? Convert to Degrees

If you need the angle in degrees:

? MySQL:

SELECT DEGREES(ACOS(0.5)) AS degrees;-- Output: 60

? PostgreSQL:

SELECT ACOS(0.5) * 180 / PI() AS degrees;-- Output: 60

?? Notes

• Input must be in the range -1 to 1 — otherwise, you'll get an error or NULL.

• Use ROUND() or FORMAT() if you want to limit decimal places.

Let me know if you want to see it used in geolocation or geometry calculations!