To Create an Arc
Click > 
Arc. The Snapping References dialog box opens. Use the arrow icon in the dialog box to add any references you want to set up before you sketch. You can also create an arc by doing the following:
Arc. The Snapping References dialog box opens. Use the arrow icon in the dialog box to add any references you want to set up before you sketch. You can also create an arc by doing the following:• Selecting an endpoint that is tangent to another open entity (that is, not a circle or an ellipse)
• Selecting any three points that lie on the arc
• Using the arc center and two endpoints
• Using the arc center, a start point, and an angle that strokes the arc from the start point in a counterclockwise direction
• Making it tangent to three other entities
• Making it tangent to two other entities, with a specified radius