Atan2()

The Atan2() function returns the arctangent value of the y/x value.

Syntax

result := math.Atan2(y,x)

Notes on Atan2():

• The ratio of the two arguments (y/x) is used to calculate the value of the arctangent.
• The result will be between -π/2 to π/2 radians.
• The value returned will be of type float64.

Special Cases

NAN:

• Atan2(y, NaN) = NaN
• Atan2(NaN, x) = NaN

(+-)0:

• Atan2(+0, x>=0) = +0
• Atan2(-0, x>=0) = -0
• Atan2(y, +Inf) = +0

(+-)π:

• Atan2(+0, x<=-0) = +π
• Atan2(-0, x<=-0) = -π
• Atan2(y>0, -Inf) = +π
• Atan2(y<0, -Inf) = -π

(+-)π/2:

• Atan2(y>0, 0) = +π/2
• Atan2(y<0, 0) = -π/2
• Atan2(+Inf, x) = +π/2
• Atan2(-Inf, x) = -π/2

(+-)π/4:

• Atan2(+Inf, +Inf) = +π/4
• Atan2(-Inf, +Inf) = -π/4

(+-)3π/4:

• Atan2(+Inf, -Inf) = 3π/4
• Atan2(-Inf, -Inf) = -3π/4

Example

The following code calculates the arctangent and prints out the result:

package main

import (
  "fmt"
  "math"
  )

func main() {

    x := math.Atan2(-77, 33)
    fmt.Println(x)

    y := math.Atan2(33, math.NaN())
    fmt.Println(y)
}

The output will be:

-1.1659045405098132
NaN