You may consider all the angles but to measure them you'll need this semicircular instrument
[DOC] [TLE] Measuring angles using a protractor | Angles | Geometry ... [PAR] Sep 22, 2011 - 3 minIn fact every positive angle has a negative counterpart, so to speak, which you can obtain by ... [DOC] [TLE] Protractor - Wikipedia [PAR] A protractor is a measuring instrument, typically made of transparent plastic or 
glass, for measuring angles.