Definition 5.1. An angle is a union of two distinct, non-opposite rays intersecting at their endpoints. Definition 5.2. An angle is an intersection of two (distinct) half-planes. Definition 5.3. An angle is the amount of turn between two lines. 1. Draw a few examples of angles according to each definition. Do the definitions match your understanding of angles? Discuss what advantages each definition may have if it were used as a definition in secondary classroom. What disadvantages might it have?