1. Section 2-4: Biconditionals and Good Definitions
Rigor – Write Biconditional statements and differentiate between a good or bad definition.
Relevance – Develop logical reasoning skills; including precision, clarity, and truth; needed to defend ideas and theories.

2. Notes: Biconditional Statements
A biconditional statement is a single true statement that combines a true conditional with its true converse.
Notation: or p iff q (“if and only if”)
Example: Two angles are supplementary if and only if the sum of their measures is 180o.

3. Ex: Write the converse, list the truth values, & write biconditional if possible.
Conditional: “If 2 angles have equal measures, then the angles are congruent.”
Converse: If 2 angles are congruent, then they have equal measures.
True
True
Biconditional: Two angles are congruent if and only if they have equal measures.

4. Converse: If 2 angles are congruent, then they are vertical angles.
Ex: Write the converse, list the truth values, & write biconditional if possible.
Conditional: “If 2 angles are vertical, then the angles are congruent.”
Converse: If 2 angles are congruent, then they are vertical angles.
True
False
Biconditional is not possible because converse is false.

5. Good definitions…are they really necessary?
Draw a polygon with 4 right angles.
We will compare our drawings with the class.

6. Good definitions must:
Use clearly understood terms (common terms or already defined)
Are precise. Avoid generic words such as large and almost.
Are reversible. Any good definition can be written as a biconditional.

7. A straight angle is an angle that measures 180o.
Ex: Is this a good definition? If so, write the definition as a biconditional.
A straight angle is an angle that measures 180o.

8. Explain why the following are not good definitions.
A fish is an animal that swims.
Giraffes are animals with very long necks

9. 2-4 Classwork from the Workbook
Pg 68 #1 – 3
Pg 69 Odds
Pg 70 #1, 2
Be ready to discuss answers in 20 min

10. 2-4 Honors Assignments Primary Assignment: Quizizz
Submit answers online: join.quizizz.com by 7AM
Codes:
Period 1: Due Thursday
Period 5: Due Thursday
Period 6: Due Friday
Secondary Assignment:
Textbook page 99 #10 – 19

11. 2-4 Standard Assignments
Primary Assignment: Quizizz
Submit answers online by Friday at 7AM
Codes:
Period 2:
Period 4:
Period 7:
Secondary Assignment:
Textbook page 99 #10 – 19