Introduction to MongoDB $cos Operator

$cos is a mathematical operator in MongoDB used to calculate the cosine value of a given angle.

Syntax

The syntax of the $cos operator is as follows:

{ $cos: <angle> }

Here, <angle> is the value representing the angle and can be a number or an expression that evaluates to a number.

Use Cases

The $cos operator is commonly used to calculate the values of trigonometric functions, particularly the cosine function. In MongoDB, it can be used in the $project stage of the aggregation pipeline as well as in query operations.

Example

Suppose we have a collection trig containing angle values with the following documents:

{ "_id": 1, "angle": 30 }
{ "_id": 2, "angle": 45 }
{ "_id": 3, "angle": 60 }

To calculate the cosine values of these angles, we can use the following aggregation pipeline:

db.trig.aggregate([
  { $project: { cos: { $cos: { $degreesToRadians: "$angle" } } } }
])

In the above pipeline, we first use the $degreesToRadians operator to convert the angles to radians and pass it to the $cos operator to calculate the cosine value. The output of the pipeline is as follows:

{ "_id": 1, "cos": 0.8660254037844386 }
{ "_id": 2, "cos": 0.7071067811865476 }
{ "_id": 3, "cos": 0.5000000000000001 }

Conclusion

The $cos operator is a mathematical operator in MongoDB used to calculate the cosine value of a given angle. It can be used in the $project stage of the aggregation pipeline as well as in query operations.