Developing Drawing Strategies: Part 2 - AutoCAD 2011 and AutoCAD LT 2011: No Experience Required - page 232

FiGuRE 5.73 Use Polar Tracking and direct input to draw the diagonal line.
Fillet these two corners.
FiGuRE 5.74 Fillet the two corners that extend into the cabin.
FiGuRE 5.75 The completed floor plan zoomed to fill the screen