Writing a Two-Column Proof
A two-column proof is a mathematical proof that uses a two-column format to organize the statements and justifications. The left column contains the statements, and the right column contains the justifications for those statements.
Writing a Two-Column Proof
To write a two-column proof, follow these steps:
- Identify the given information. What information is given to you? This information should be listed in the left column of your proof, with the justification "Given" in the right column.
- State the conclusion. What are you trying to prove? This statement should be listed in the left column of your proof, with the justification "To prove" in the right column.
- Use logical reasoning to create a chain of statements that leads from the given information to the conclusion. Each statement in the chain should be justified by a previously stated statement, a definition, a postulate, or a previously proven theorem.
- Check your proof. Make sure that each statement in your proof is justified and that the chain of reasoning is logical.
Examples of Two-Column Proofs
Here are some examples of two-column proofs:
Example 1
Given: Line segment AB is parallel to line segment CD.
To prove: Angles A and D are congruent.
Proof:
Statement | Justification ---|--- Line segment AB is parallel to line segment CD. | Given Angles A and D are alternate interior angles. | Definition of parallel lines Angles A and D are congruent. | Congruence of alternate interior angles
Example 2
Given: Angle ABC is a right angle.
To prove: The measure of angle ABC is 90 degrees.
Proof:
Statement | Justification ---|--- Angle ABC is a right angle. | Given The measure of a right angle is 90 degrees. | Definition of a right angle The measure of angle ABC is 90 degrees. | Transitive property of equality
Questions About Two-Column Proofs
Question 1: What are the benefits of using a two-column proof?
Answer: There are several benefits to using a two-column proof. First, it helps to organize your thoughts and make your proof easier to follow. Second, it helps to ensure that your proof is logical and complete. Third, it can help you to identify any errors in your reasoning.
Question 2: What are some common mistakes that students make when writing two-column proofs?
Answer: Some common mistakes that students make when writing two-column proofs include:
- Forgetting to include the given information in the left column.
- Stating the conclusion in the wrong column.
- Using invalid justifications.
- Making logical errors in their reasoning.
Question 3: How can I improve my skills at writing two-column proofs?
Answer: There are several things you can do to improve your skills at writing two-column proofs. First, practice writing proofs on a variety of topics. Second, get feedback from your teacher or a tutor. Third, read proofs written by other students or mathematicians.
Conclusion
Two-column proofs are a valuable tool for learning and understanding mathematics. By following the steps outlined in this article, you can write clear and concise two-column proofs that will help you to demonstrate your understanding of mathematical concepts.