You can perform the same construction much more easily using the  'angle with fixed size' tool Angle with fixed size

You do not use this tool to read the angle at B and create the same angle. This would be inaccurate. Instead, you tell the fixed angle to take the size of the other angle.

 

Transfer the angle at B to the point B* as shown.

  • Choose the icon for "angle with fixed size".
  • Click anywhere on the black ray starting from B* and create A*.
  • Click on B*.
  • Click anywhere in the window. 
  • A dialog box will open.
  • In this dialog, you press the "Set Size ..." button on the bottom row. The dialog closes.
  • Now click on A, B and then on C, or simply on the arc that represents angle <ABC..
  • Done!

This is the last assignment in the tutorial.