8. Conditional Statements

For September 9th class

8.  CONDITIONAL STATEMENTS
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LO:  SWBAT will determine the validity of a conditional statement, its converse, inverse
and contrapositive.
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(Textbook Chapter 2-3, starting from page 91)


1. Conditional Statements
To change a statement to an If-Then statement is to make a conditional statement.  

Let's look at the statement:  "Rain means it's cloudy."
Changing this to a conditional means identifying the hypothesis and conclusion then adding the if-then words to it like this:
 

The "if" is always followed by the hypothesis and the "then" is always followed by the conclusion.

Now you try.  Rewrite these advertisements into If-Then forms:

2.  Converse, Inverse, and Contrapositive
Other statements based on the conditional statements are Converse, Inverse and Contrapositive.  They are formed by exchanging and negating the hypothesis and conclusion of the conditional statements in various ways.

Notice that the symbols for the Conditional Statement reads as "p to q".

Now you try: using the same conditionals from the advertisements from section 1 above, write each one's converse, inverse and contrapositive.

3.  Counterexample
A Counterexample is a true example to prove a statement false.

For example:
Statement:  "If it has four right angles, then it's a square"
This is a false statement.  We then give the counterexample:  A rectangle.

The counterexample proves that the statement was false.

Now you try:  for each false statement from #2 above, provide a counterexample.

4.  Biconditional Statements

A conjunction of two statements where both the conditional and its converse are true is called biconditional. 

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Homework
Page 94, questions 1-10