accurately measure angles by numbers

You can do this by using the transformation tools in combination with the alignment tools.

Here is an example procedure:

1. Draw a horizontal line segment using the "Draw bezier curves and straight lines" tool. You can hold down the control key to constrain it to be horizontal.

2. Duplicate that line. (Ctrl-D)

3. Select from the menu: Object>Transform... (or, Shift-Ctrl-M), to open the Transform panel.

4. In the transform panel, click the "Rotate" tab, enter the desired angle, and apply. I picked 33 degrees.

You now have two lines separated by the desired angle. If you'd like to combine them into a single object that just contains the angle, here's how to do it:

1. Select both objects by dragging a selection rectangle around both, or by shift-clicking (as per usual, to select multiple items).

2. Select from the menu: Object>Align and distribute... (or, Shift-Ctrl-A), to open the Align and Distribute panel.

3. Click the correct two icons to line up the desired corners. For the 33-degree angle, and joining them on the left hand side, that would be "Align left edges" and "Align bottom edges."

4. Select from the menu Path>Combine (or Ctrl-K) to join the two segments into a single path object.