Transcript dog law

Deductive Reasoning (G.1d)
Obj: SWBAT apply the laws of validity: Detachment,
Contrapositive & Syllogism and the symbolic form (2.4).
Warm-Up: Day 17 worksheet, illustrate the “given” statements in
the form of Venn Diagrams; 1st NW packet
**hw/hw log/storybook: “Logic”/Nine Weeks packet
Homework (day 20)
Validity worksheet/1st NW packet complete/Quiz next block
Study for 1st Nine Weeks Test-(prior tests/quizzes/Sol questions from binder)
Storybook grade: “Logic” and 1st NW Reflection
Pearson due Friday/Online Extra Credit will close on Oct 31st
Extra Credit- 1st NW
Since the VA Benchmark was not loading,
I have substituted NATIONAL
Benchmark 2 in lieu of the VA benchmark.
 This will close on Oct 31
 If you would like me to enter it, after you
take it, give me a piece of paper with your:
name, block and tell me you want me to
record it into HAC as a quiz grade.

Copy into SOL Binder (G.1)- day 20
Let p = “a dog eats bread”
Let r = “the dog gets fat”
Let q = “the dog gains weight”
1) p → q, “If a dog eats bread, then the dog gains weight” is a true
statement. John’s dog eats bread. What can be concluded? Justify.
John’s dog gains weight. Law of Detachment.
2) p → q means “If a dog eats bread, then the dog gains weight.” p → q
is a true statement.
State the contrapositive. Is it a true statement?
“If the dog does not gain weight, then the dog does not eat bread” is a
true statement.
3) p → q means “If a dog eats bread, then the dog gains weight.”
q → r means “If the dog gains weight, then the dog gets fat.”
Using the law of syllogism, what is the logical conclusion?
“If a dog eats bread, then the dog gets fat.”
Determine what, if anything can be concluded. Justify.
1. If two angles are vertical, then they do not form a linear pair.
If two angles are vertical, then they are congruent.
2. If you eat to live, then you live to eat. Paula does not live to eat.
3. Cars are useful. Useful cars are practical. We have a Kia.
Determine if the statements are valid or invalid. Justify.
1. In-line skaters live dangerously. If you live dangerously, then you like to dance.
If you are an in – line skater, then you like to dance.
2. If you drive safely, the life you save may be your own. The life Casey saves may not
be her own. She does not drive safely.
3. If a figure is a rectangle, then its opposite sides are congruent.
AB  DC and AD  BC. ABCD is a rectangle.
Law of Contrapositive
Law of Contrapositive: If p → q is true and q is
not true, then p is not true.
Symbolic Representation: p → q
~q
~p
Ex:
If you do your home work, then you will pass
this class. Shane did not pass the class.
Shane did not do his homework
Law of Detachment
Law of Detachment- If the Hypothesis of a conditional
statement is true, then the conclusion is also true.
If p → q is true and p is true, then q is true.
Symbolically: p → q
p
q
Ex:
 Angles that are supplementary have measures with a
sum of 180°. < A and < B are Supplementary
< A and < B measures are a sum of 180°

Law of Syllogism
Law of Syllogism: If hypothesis p, then conclusion q.
If hypothesis q , then conclusion r.
(if both above statements are true)
If hypothesis p, then conclusion r.
(Then the above is also true)
Symbolically: p → q
q→r
pr
Ex:
 The sun is a star. Stars are in constant motion. The
sun is in constant motion.
The sun is in constant motion
