VB & VBA in a Nutshell: The Language

Atn Function

Named Arguments

No

Syntax

Atn(number)

number

Use: Required

Data Type: Numeric

Any numeric expression, representing the ratio of two sides of a right angle triangle.

Return Value

The return value is a Double data type representing the arctangent of number, in the range –pi/2 to pi/2 radians.

Description

Takes the ratio of two sides of a right triangle (number) and returns the corresponding angle in radians. The ratio is the length of the side opposite the angle divided by the length of the side adjacent to the angle.

Rules at a Glance

• If no number is specified, a runtime error is generated.

• The return value of Atn is in radians, not degrees.

Example

Private Sub CommandButton1_Click()

    Dim dblSideAdj As Double
    Dim dblSideOpp As Double
    Dim dblRatio As Double
    Dim dblAtangent As Double
    
    dblSideAdj = 50.25
    dblSideOpp = 75.5
    
    dblRatio = dblSideOpp / dblSideAdj
    dblAtangent = Atn(dblRatio)
    'convert from radians to degrees
    dblDegrees = dblAtangent * (180 / 3.142)
    MsgBox dblDegrees & " Degrees"

End Sub

Programming Tips and Gotchas

• To convert degrees to radians, multiply degrees by pi/180.

• To convert radians to degrees, multiply radians by 180/pi.

• Don't confuse Atn with the cotangent. Atn is the inverse trigonometric function of Tan, as opposed to the simple inverse of Tan.

See Also

Tan Function