Returns the start angle of the elliptical figure (ellipse or arc) in radians (DXF 50).

The start angle is measured counterclockwise from the major axis. When (StartAngle = 0) and (EndAngle = Oda2PI) and (EndAngle - StartAngle) > 1e-6, the figure is closed, that is an ellipse.

Example of Working with the Elliptical Arc 

Specific Elliptical Arc Properties 

OdDbEllipse::setStartAngle() method 

OdDbEllipse::endAngle() method