$tan (aggregation)

• $tan

New in version 4.2.

Returns the tangent of a value that is measured in radians.

$tan has the following syntax:

{ $tan: <expression> }

$tan takes any valid expression that resolves to a number. If theexpression returns a value in degrees, use the$degreesToRadians operator to convert theresult to radians.

By default $tan returns values as a double.$tan can also return values as a128-bit decimalas long as the <expression> resolves to a 128-bit decimal value.

For more information on expressions, seeExpressions.

Behavior

null, NaN, and +/- Infinity

If the argument resolves to a value of null or refers to a fieldthat is missing, $tan returns null. If theargument resolves to NaN, $tan returns NaN.If the argument resolves to negative or positive infinity,$tan throws an error.

"errmsg" :  "Failed to optimize pipeline :: caused by :: cannot  apply $tan to -inf, value must in (-inf,inf)"

Example

• Tangent of Value in Degrees
• Tangent of Value in Radians

The trigonometry collection contains a document thatstores one side and one angle in a right-angle triangle:

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("53.13010235415597870314438744090659"),
  "side_a" : NumberDecimal("3")
}

The following aggregation operation uses the$tans expression to calculate the side oppositeto angle_a and add it to the input document using the$addFields pipeline stage.

db.trigonometry.aggregate([
  {
    $addFields : {
      "side_b" : {
        $multiply : [
          { $tan : {$degreesToRadians : "$angle_a"} },
          "$side_a"
        ]
      }
    }
  }
])

The $degreesToRadians expression converts thedegree value of angle_a to the equivalent value in radians.

The command returns the following output:

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("53.13010235415597870314438744090659"),
  "side_a" : NumberDecimal("3")
  "side_b" : NumberDecimal(4.000000000000000000000000000000000")
}

Since angle_a and side_a are stored as128-bit decimals, the output of$tan is a 128-bit decimal.

The trigonometry collection contains a document thatstores the hypotenuse and one angle in a right-angle triangle:

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("0.9272952180016122324285124629224288"),
  "side_a" : NumberDecimal("3")
}

The following aggregation operation uses the$tan expression to calculate the side adjacentto angle_a and add it to the input document using the$addFields pipeline stage.

db.trigonometry.aggregate([
  {
    $addFields : {
      "side_b" : {
        $multiply : [
          { $tan : "$angle_a" },
          "$side_a"
        ]
      }
    }
  }
])

The command returns the following output:

{
  "_id" : ObjectId("5c50782193f833234ba90d85"),
  "angle_a" : NumberDecimal("0.9272952180016122324285124629224288"),
  "side_a" : NumberDecimal("3")
  "side_b" : NumberDecimal("3.999999999999999999999999999999999")
}

Since angle_a and side_a are stored as128-bit decimals, the output of$tan is a 128-bit decimal.