Section 2-2 (cont.) Definitions

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Section 2-2 (cont.)Definitions
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Definition Activity

• Work with your surrounding classmates and write
  the definition for a Polyglob.

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Good Definitions

• A good definition uses clearly understood terms.
  The terms should be commonly understood or
  already defined.
• A good definition is precise. Good definitions
  avoid words such as large, sort of, and almost.
• A good definition is reversible. That means that
  you can write a good definition as a true
  biconditional.

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Example (Me)

• Show that this definition of perpendicular lines
  is reversible. Then write it as a true
  biconditional.
• Definition Perpendicular lines are two line that
  intersect to form right angles.
• Conditional If two lines are perpendicular, then
  they intersect to form right angles.
• Converse If two lines intersect to form right
  angles, then they are perpendicular.
• Biconditional Two lines are perpendicular if and
  only if they intersect to form right angles.

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Example (We)

• Definition An airplane is a vehicle that flies.
• Conditional
• Converse

If it is an airplane, it is a vehicle that flies.
True
If it is a vehicle that flies, then it is an
airplane.
False counterexample helicopter
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Example (You)

• Definition A right angle is an angle whose
  measure is 90.
• Conditional
• Converse
• Biconditional

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HomeworkSection 2-2p.90s 18-23, 33-37