[2 Tangents, Radius] command will generate an arc by specifying
While
"Specify 1st base line"
prompt is displayed, specify around a point on a curve where the generating
arc's end point will touch
While
"Specify 2nd base line"
prompt is displayed, specify around a point on a curve where the generating
arc's the other end point will touch
Press OK button after inputing the radius in the daialogue box.