Skip to main content
Documents
Basic SyntaxMath FunctionsDate FunctionsJSON FunctionsDatabasesTables & Schema ManagementString FunctionsTriggersIndexes

PostgreSQL COS

The `COS` function in PostgreSQL is a mathematical function used to calculate the cosine of a specified angle, which is provided in radians. It is commonly utilized in trigonometric calculations within SQL queries to compute angular relationships and transformations.

Usage

The `COS` function is used when you need to determine the cosine of an angle in radians, which is essential in various analytical and geometrical computations. The syntax is simple and involves passing a numeric value, representing the angle in radians, as the argument.


COS(radians)

Here, `radians` is a numeric expression denoting the angle for which the cosine value is to be calculated. The result of the `COS` function ranges from -1 to 1.

Examples

1. Basic Cosine Calculation


SELECT COS(0);

In this example, the `COS` function calculates the cosine of `0` radians, which returns `1`.

2. Calculation with Variable


SELECT COS(angle_column)
FROM angles_table;

This example retrieves the cosine of angles stored in the `angle_column` of the `angles_table`, allowing dynamic computation based on table data.

3. Use in Geometric Transformation


SELECT point_id, x * COS(rotation_angle) - y * SIN(rotation_angle) AS transformed_x
FROM points_table;

Here, the `COS` function is used in conjunction with `SIN` to perform a rotation transformation on points stored in `points_table`, showcasing its application in geometric algorithms.

Tips and Best Practices

  • Ensure angles are in radians. The `COS` function requires input in radians; convert degrees to radians if necessary using the formula: degrees * π / 180.
  • Use with other trigonometric functions. Combine `COS` with `SIN` and `TAN` for comprehensive trigonometric calculations.
  • Optimize performance with indexed columns. When using `COS` in queries involving tables, ensure the angle columns are indexed for better performance.
  • Consider precision. Be aware of the floating-point precision, which can affect results in highly-sensitive calculations. PostgreSQL handles floating-point operations with double precision.
  • Handle non-numeric values. Ensure that the input to the `COS` function is numeric to prevent errors. Consider using a `CASE` statement or `COALESCE` function to handle or filter out non-numeric values appropriately.