The ACOS() function in SQLite is used to calculate the arc cosine (inverse cosine) of a given numeric value. The result is the angle in radians whose cosine is the specified number.

Syntax

ACOS(X)

Where X is the numeric value for which you want to calculate the arc cosine. It must be in the range -1 to 1 because these are the only values for which cosine values are defined.

The result will be an angle in radians between 0 and π (3.14159…).

Example 1

Here’s a quick example to demonstrate how it works:

SELECT ACOS(0.32);

Output:

1.24506683950027

Example 2

Suppose we have a table angles with a column cos_value that contains cosine values, and we want to find the corresponding angle in radians for these values.

CREATE TABLE angles (cos_value REAL);

INSERT INTO angles (cos_value) VALUES (1), (0.5), (0), (-0.5), (-1);

Now, we can use ACOS() to calculate the angles for each cosine value:

SELECT cos_value, ACOS(cos_value) AS angle_in_radians
FROM angles;

Output:

cos_value  angle_in_radians
---------  ----------------
1.0        0.0             
0.5        1.0471975511966 
0.0        1.5707963267949 
-0.5       2.0943951023932 
-1.0       3.14159265358979

In this example:

• When cos_value is 1, the angle is 0 radians (cosine of 0 radians is 1).
• When cos_value is 0.5, the angle is approximately 1.0471975511966 radians.
• When cos_value is 0, the angle is approximately 1.5707963267949 radians (π/2), as the cosine of π/2 is 0.
• Similarly, -1 corresponds to π radians, or approximately 3.14159265358979.