# ICurve.QueryTangent Method

Constructs a line tangent to a curve from a point at a specified distance along the curve.

[Visual Basic .NET]
**Public Sub QueryTangent ( _**
**ByVal** *extension*** As **esriSegmentExtension, _
**ByVal** *DistanceAlongCurve*** As **Double, _
**ByVal** *asRatio*** As **Boolean, _
**ByVal** *Length*** As **Double, _
**ByVal** *tangent*** As **ILine _
**)**

[C#]
**public **void** QueryTangent (**
esriSegmentExtension *extension,*
double *DistanceAlongCurve,*
bool *asRatio,*
double *Length,*
ILine *tangent*
**);**

[C++]
**HRESULT QueryTangent(**
**esriSegmentExtension** extension,
**double** DistanceAlongCurve,
**VARIANT_BOOL** asRatio,
**double** Length,
**ILine*** tangent
**);**

[C++]
**Parameters**
*extension*

* extension* is a parameter of type **esriSegmentExtension**
*DistanceAlongCurve*

* DistanceAlongCurve* is a parameter of type **double**
*asRatio*

* asRatio* is a parameter of type **bool**
*Length*

* Length* is a parameter of type **double**
*tangent*

* tangent* is a parameter of type **ILine***

#### Product Availability

Available with ArcGIS Engine, ArcGIS Desktop, and ArcGIS Server.

#### Description

Given a distance along the curve specified either as a ratio of the length or as a specific fixed distance, QueryTangent returns the Line tangent to the Point. The length and method of tangential extension of the tangent line are given by the user. The method of tangential extension determines the direction of the tangent line as though it were being extended at a From point or a To point.

#### Remarks

#### See Also

ICurve Interface | ILine Interface