From Xojo Documentation

Property (As Double )
aArcShape.ArcAngle = newDoubleValue
DoubleValue = aArcShape.ArcAngle

Supported for all project types and targets.

The angle of the arc, in radians.

Sample Code

The following method, when called from the Paint event of a Window, creates an arc.

Dim a As New ArcShape
a.ArcAngle = 1.57
a.StartAngle = -1.57
a.FillColor = RGB(255, 0, 127)
g.DrawObject(a, 100, 100)