If two 90 degree angles are placed back-to-back (Figure 5), they total 180 degrees. ... Copy the angles with the method described above in "Copying an Angle" (or use a protractor). Figure 15. Figures ...

An obtuse angle is an angle that is bigger than 90° degrees, but doesn’t reach a straight line at 180°. ... Let's have a go at using a protractor to measure some angles.