"Start, End, Direction" command will generate an arc by
specifying two ends and the direction at the start.
While
"Specify Start point of arc"
prompt is displayed, specify the start point of the arc to generate.
While
"Specify End point of arc"
prompt is displayed, specify the End point of the arc to generate.
While
"Specify tangent direction"
prompt is displayed, specify the tangent direction at the start. Preview of the
arc size changing can be seen following to the mouse movement.