# Asin Function

 Asin Function

System.Math

#### Syntax

```Math.Asin(

d

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

A number representing a sine, which can range from -1 to 1

#### Return Value

A Double between -pi/2 and pi/2 that is the arcsine of d in radians

#### Description

Returns the arcsine of d , in radians

#### 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.

#### Programming Tips and Gotchas

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

#### VB.NET/VB 6 Differences

The Asin function did not exist in VB 6.

Acos Function, Atan Function, Atan2 Function

 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 dblSideOpp As Double

Dim dblRatio As Double

Dim dblAtangent As Double

dblSideOpp = 75.5

dblAtangent = Math.Atan(dblRatio)

dblDegrees = dblAtangent * (180 / 3.142)

MsgBox dblDegrees & " Degrees"

End Sub
```

#### Programming Tips and Gotchas

• 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.

Acos Function, Asin Function, Atan2 Function

 Atan2 Function

System.Math

#### Syntax

```Math.Atan2(

y

,

x

)
```
x (required; Double)

The x coordinate of a point

y (required; Double)

The y coordinate of a point

#### Return Value

A Double that is the arctangent of the ratio x/y, in radians

#### Description

Returns the angle in the Cartesian plane formed by the x-axis and a vector starting from the origin (0,0) and terminating at the point (x, y). More specifically , the return value q satisfies the following:

• For (x, y) in quadrant 1, 0 < q < pi/2.

• For (x, y) in quadrant 2, pi /2 < q < pi.

• For ( x, y) in quadrant 3, -pi < q < -pi /2.

• For ( x, y) in quadrant 4, -pi /2 < q < 0.

#### Rules at a Glance

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

#### VB.NET/VB 6 Differences

The Atan2 function does not exist in VB 6.

Acos Function, Asin Function, Atan Function

 AttributeUsage Attribute

#### Class

System.AttributeUsageAttribute

Class

#### Description

Defines the program elements to which a custom attribute can be applied. Its use is required when defining a custom attribute.

#### Constructor

```New(

validOn

)
```
validOn ( System.AttributeTargets )

Indicates the program elements to which a custom attribute can be applied. Possible values are All , Assembly , Class , Constructor , Delegate , Enum , Event , Field , Interface , Struct , Method , Module , Parameter , Property , and ReturnValue .

#### Properties

AllowMultiple (Boolean)

Indicates whether the attribute can be used more than once on a single program element. Its default value is False .

Inherited (Boolean)

Indicates whether attribute is automatically inherited by derived classes and overridden members . Its default value is True .

ValidOn ( AttributeTargets enumeration)

Read-only. Indicates the program elements to which the attribute can be applied. Its value is set by the required validon parameter of the class constructor.

#### Example

See Section 8.2 in Chapter 8 for more details and an example.