Source: Discovering Geometry by Michael Serra

Define a “good definition”Identify counterexamples when

possibleState converses of definitionsDefine a right angle and an acute

angle

A good definition...is precise.

places an object to be defined into a class of well-defined similar things

is able to state how different an object is from the other members of the class.

STEPS:

1. Classify

2. Differentiate

3. Test

Let’s recall our SETS.

Is this a well-defined set?

the set of famous songs of Michael Jackson released from 1980 – 1990

the set of numbers between -3 and 3

Definition:

A polygon with exactly six sides is a hexagon.

Re-state the definition…

A hexagon is a polygon with exactly six sides.