Interface > Working with Digitized Input > To Convert a Chain
  
To Convert a Chain
You can convert a chain to an arc or a single straight line pressing 8 in Input mode. This enables you to digitize a number of points to approximate an arc, or for a long line when necessary to account for warpage. Then convert the chain into exact entities.
You can convert a green chain to a line, and a purple chain to an arc.
1. Place the cursor near a point on the chain to convert, press 8.
2. From the menu, select arc or line.