Measure tool

While the Measure tool [U] is pretty handy for measuring distances (especially on a diagonal),
you can also use it to measure angles (like a protractor). Make sure the Info palette [F8] (Window
» Show Info) is visible. Select the Measure tool [U]: click and drag to draw a line. Hold down the
Alt key and drag a second line out from one of the end nodes (note the angle and lengths of the
two lines in the Info palette)