Engineering Specialist Allen S. Jessup writes about a feature in AutoCAD that allows us to draw tangent lines and arcs.

"If you need to create lines that are tangent to arcs, or arcs tangent to lines at their endpoints, you can use a function available in AutoCAD since its release. To create an arc tangent to the endpoint of a line, first draw the line, then start the Arc command. When asked for the start point of the arc, press Enter. You should see the rubber-band arc attached to the line that was just drawn. You can either pick a point for the end of the arc or move the cursor in the direction you want the arc to go and enter a chord distance.

"Conversely, if you need to create a line tangent to the endpoint of an arc, draw the arc first, then start the Line command and press Enter when asked for the start point. The line will snap to the endpoint of the arc and you will see from the rubber-band line that you are constrained to tangency. Either pick an endpoint or enter a length for the line."
 
Notes from Cadalyst Tip Patrol: Drawing linework the way it needs to be is the name of the game. This feature in AutoCAD is great as long as you draw the line, then the arc, or vice-versa. If you need to draw a line tangent to an arc, but the arc has been there for some time, use the tangent osnap. There is also a command to draw an arc tangent to the last arc drawn: use the Continue Arc command in the ribbon.