Introduction to MongoDB $atan Operator

$atan is a mathematical operator in MongoDB used to calculate the arctangent of a given number. The arctangent function is a trigonometric function that returns an angle whose tangent is equal to the given number. In MongoDB, the result of $atan is returned in radians.

Syntax

The syntax of $atan operator is as follows:

{ $atan: <number> }

Here, <number> is a valid number, which can be a number, field reference, variable or other mathematical expressions.

Use Cases

The $atan operator is typically used to calculate an angle whose tangent is equal to a given number. For example, it can be used to calculate the angles of a set of triangles.

Example

Assume we have a collection triangle that contains the lengths of two sides a and b of each triangle. Now we need to calculate the angle angle of each triangle. We can use the $atan operator to accomplish this task. Here is an example:

db.triangle.aggregate([
  {
    $project: {
      a: 3,
      b: 4,
      angle: { $atan: { $divide: ["$a", "$b"] } }
    }
  }
])

In this example, the $project stage uses the $divide operator to calculate the quotient of the two sides a and b of the triangle, and then uses the $atan operator to calculate the arctangent value, which is then stored in the angle field. Assuming the two sides of the triangle are 3 and 4, the calculated angle should be 0.6435.

Conclusion

The $atan operator is a mathematical operator in MongoDB used to calculate the arctangent of a given number. It can be used to calculate the angles of triangles or other tasks involving trigonometric functions.