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VBScript in a Nutshell, 2nd Edition by Ron Petrusha, Matt Childs, Paul Lomax

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Name

Atn Function

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 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

<%   
Const Pi = 3.14159
 Dim dblSideAdj, dblSideOpp 
 Dim dblRatio, dblAtangent, dblDegrees

 dblSideAdj = 50.25
 dblSideOpp = 75.5
    
 dblRatio = dblSideOpp / dblSideAdj
 dblAtangent = Atn(dblRatio)
 ' convert from radians to degrees
 dblDegrees = dblAtangent * (180 / Pi)
 Response.Write dblDegrees & " Degrees"
%>

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

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