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Atan Function

System.Math

## Syntax

`Math.Atan(`d`)`
`d `(required; Double or any valid numeric expression)

A number representing a tangent

## Return Value

A Double that is the arctangent in radians of `d`, in the range -pi/2 to pi/2

## Description

Takes the ratio of two sides of a right triangle (`d`) 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 `d` is out of range, the function returns `NaN`.

• This is a Shared member, so it can be used without creating any objects.

## Example

```Private Sub Main(  )

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 = Math.Atan(dblRatio)
'convert from radians to degrees
dblDegrees = dblAtangent * (180 / 3.142)
MsgBox dblDegrees & " Degrees"

End Sub```

## Programming Tips and Gotchas

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

• Do not confuse Atan with the cotangent. Atan is the inverse trigonometric function of Tan, whereas the cotangent is the reciprocal of the tangent.

## VB.NET/VB 6 Differences

The Atan function corresponds to the VB 6 Atn intrinsic function.

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