Laws of Detachment and Syllogism

Geometry

Using the conditional statement below, write a paragraph explaining…◦ How to find the converse◦ How to determine the truth value of the conditional◦ How to determine the truth value of the converse◦ How to determine if you can write a biconditional and

if you can, how would you write it

“If two lines are parallel, then they are coplanar”

(at least one sentence per bullet)

Journal Prompt – “Conditionals”

Law of Detachment: If a conditional is true and its hypothesis is true, then its conclusion is true.

If p q is a true statement and p is true, then q is true

2.3 Laws of Detachment and Syllogism

1. Given: If an angle is obtuse, then its measure is

greater than 90⁰. Angle A is obtuse.

Conclusion: The measure of angle A is greater than 90⁰.

Use the Law of Detachment to draw a conclusion. If it is not possible to draw a conclusion based on the given information write not possible

2. Given: If an angle is obtuse, then its measure is

greater than 90⁰. The measure of angle A is greater than

90⁰.

Conclusion: Cannot draw a conclusion. You are only told the conclusion of the statement above is true.

Law of Syllogism: If p q and q r are true statements, then p r is a true statement.

Given: If angles are a linear pair, then they are

supplementary. If angles are supplementary, then their sum is 180⁰.

Conclusion: If angles are a linear pair then their sum is 180⁰.

Use the Law of Syllogism to draw a conclusion.

Law Worksheet

QUIZ Monday!!!

Homework