1
Opener:Study the following pattern.
1. If the pattern is extended, findthe terms in row 7.
2. Make a conjecture for the pattern.
3. Make a conjecture for the sum of the terms in each row.
Row 1: 1Row 2: 1 1Row 3: 1 2 1Row 4: 1 3 3 1Row 5: 1 4 6 4 1Row 6: 1 5 10 10 5 1
2
Homework Questions:
3
2‐2: Conditional StatementsWhat are they?
Examples:
1) If you are 16, then you are a teenager.
2) You live in Illinois, if you live in Northbrook.
Venn Diagrams to represent conditionals:
1) If you are 16, then you are a teenager.
2) You live in Illinois, if you live in Northbrook.
Conditional Statements
Hypothesis Conclusion
Notation Venn Diagram
4
Writing Conditional Statements:
1) Tarantulas are spiders.
2) A 25 degree angle is acute.
Analyzing truth values:
1) If this is September, then the next month is October.
2) If 2 angles are obtuse, then they are congruent.
3) If an even number greater than 2 is prime, then 5 + 4 = 8.
Important conclusion:
If p is true, then ___________________________________
If p is false, then __________________________________
5
Examples:1) FACT: Glenbrook North students are Spartans.
Conditional:
Converse:
Inverse:
Contrapositive:
2) Conditional:If m A = 95 degrees, then A is obtuse. TRUE or FALSE
Converse: TRUE or FALSE
Inverse: TRUE or FALSE
Contrapositive: TRUE or FALSE
Look for the pattern (what kind of reasoning?):
Which statements always have the same truth value?
RelatedConditionals
Negation Converse
Inverse Contrapositive
6
2‐3: Deductive Reasoning
A process of using logic to draw conclusions from given facts, definitions, and properties
How is this different from inductive reasoning?
Inductive or Deductive?
1)
2) There is a myth that birds will abandon their young if you touch them.
7
Types of Deductive Reasoning
Law of Detachment Law of Syllogism
If p q is a true statement,and p is true,then q is also true.
If p q and q r, aretrue statements, thenp r is a true statement.
Example: If I get overa 90%, then I get an A.I got a 96%.Conjecture: I got an A.
Example: If I oversleep, then I will miss the bus.If I miss the bus, then Iwill have to walk to school.Conjecture: If I oversleepthen I will have to walk toschool.
8
With your partner, decide whether each of the following examples is valid using Deductive Reasoning. Then decide which law it is demonstrating. Hold up the appropriate response cards.
A) Given: If side lengths of a triangle are 5, 12, and 13, then the area of the triangle is 30. The area of PQR is 30.Conjecture: The side lengths of the triangle are 5, 12, and 13.
B) Given: In the World Series, if a team wins 4 games, the team wins the Series. In 2004, the Red Sox won 4 games in the World Series.Conjecture: The Red Sox won the World Series.
C) Given: If a figure is a kite, then it is a quadrilateral. If a figure is a quadrilateral, then it is a polygon.Conjecture: If a figure is a kite, then it is a polygon.
D) Given:If a number is divisible by 2, then it is even. If a number is even, then it is an integer.Conjecture: If a number is an integer, then it is divisible by 2.
9
Draw a conclusion using Deductive Reasoning:
A) Given: If 2y = 4, then z = ‐1. If x + 3 = 12, then 2y = 4. x + 3 = 12.
Conclusion:
B) Given: If the sum of two angles is 180 degrees, then the angles are supplementary. If 2 angles are supplementary, then they are not the angles in a triangle.m<A = 135 degrees and m<B = 45 degrees
Conclusion:
10
For the following scenarios, discuss the given statements, and decide with your partner if they are an example of a negation, a converse, an inverse, or a contrapositive.
Then decide whether the statement is true or false. When I call time, one partner should hold up the statement response card, and the other should hold up the true/false response card.
Remember, if you think it is false, make sure you have a counterexample!
Closer:
11
Conditional: If an animal is a brown bear,then the animal sleeps for 3 months each year.
Related Statement:
If an animal does not sleep for 3 months each year,then the animal is not a brown bear.
12
Conditional: If m A = 95o, then A is obtuse.
Related Statement: If A is obtuse, then m A = 95o.
13
Has a swimming pool
Enclosed by a fence
Yard
Conditional: If a yard has a swimming pool, then it is enclosed by a fence.
Related Statement: If a yard does not have a swimming pool, then it is not enclosed by a fence.
14