Postulates and Paragraph Proofs

1
Postulates and Paragraph Proofs

• Section 2-5

2

• postulate or axiom a statement that describes a
  fundamental relationship between the basic terms
  of geometry. Postulates are accepted as true.
• proof a logical argument in which each
  statement you make is supported by a statement
  that is accepted as true.
• theorem a statement or conjecture that has
  shown to be true.

3
Postulates

• 2.3 A line contains at least 2 points.
• 2.4 A plane contains at least 3 points not on
  the same line.
• 2.5 If 2 points lie in a plane, then the entire
  line containing those points lies in that plane.

4

• 2.6 If 2 lines intersect, then their
  intersection is exactly one point.
• 2.7 If 2 planes intersect, then their
  intersection is a line.

5
Midpoint Theorem (2.8)

• If M is the midpoint of , then

B
M
A
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5 Parts of Good Proof

• State theorem or conjecture to be proved.
• List the given information.
• Draw a diagram if possible.
• State what is to be proved.
• Develop a system of deductive reasoning.