The procedure below describes how to create a new arc that is tangent to a selected entity. The new arc and the existing entity are mutually constrained. The new arc can also be constrained by additional entities in the graphical display area.
Note: If the tangent entity is not in the current sketch, you must add it to the sketch as a reference entity.
To create an arc that is tangent to a selected entity:
Select the Arc
tool 
.
The cursor appears in the graphical display
area as a crosshair-and-arc 
.
Right-click to display the popup menu, and select the Tangent option.
Click on an entity. The new arc will be tangent to the entity.
Note: Instead of using the popup menu, you can click the entity when the tangent constraint is activated - a dashed cyan line. See Alignment with Existing Entities.
Move the cursor away from the start point. An image of a tangent circle appears.
You can define an additional constraint for the new arc.
Move the cursor to determine one end point of the arc, and click.
The image of the tangent circle changes to the image of a tangent arc.
Move the cursor to determine the second end point of the arc. As you move the cursor, you can change the point of tangency on the entity selected in step 3.
Click to define the new arc.
Tip: Dynamic constraint lines can help you position the new arc relative to the XY axis or other entities.
Note: After an arc is created using the Tangent option, the Pt option is automatically selected again, ready to create an arc from a point. If you want to create another arc that is tangent to an existing entity, you must select the Tangent option again.