Proof by Contradiction Teacher Resources

In this proofs by contradiction worksheet, students solve 1 word problem about a crime.  Students use proof by contradiction to determine the criminal in the word problem.

Is it a right triangle or not? Introduce scholars to the converse of the Pythagorean Theorem with a lesson that also provides a proof by contradiction of the converse. Pupils use the converse to determine whether triangles with given...

Non-terminating. Non-recurring decimal. Irrational numbers. Proof by Contradiction? Root 2, 3, 5, 6, 7, 8. Don't be afraid to explore the impossible and check out this short video that offers a rational explanation of irrational...

Viewers of a short video use the Proof by Contradiction technique; to determine which apprentice monk swallowed which crystal the group attempted to steal from the Sacred Crystal Temple.

Students explore the concept of vertex-edge graphs.  In this vertex-edge graphs lesson, students try to construct a graph with a given diameter, number of vertices, size, and planarity.  Students construct various vertex-edge...

Try as you might, some functions just cannot be computed. The lab introduces the class to the possibility of unsolvable problems. The fourth lesson in a series of seven begins with a logic problem, then progresses to looking at functions...

Perfect cloning is impossible — and that's been proven mathematically. Investigate the complexity of cloning in physics. The video instructor explains why cloning is theoretically impossible. He uses several examples to illustrate...

Participants who use this resource will apply the Pythagorean Theorem to show whether or not the shaded triangle inscribed in a rectangle is a right triangle. Once all of the sides on the shaded triangle are found, it is important that...

Young scholars engage in a lesson that is about the classification of triangles and the mathematical proofs involved in working with them. They work on a variety of problems that are created by the teacher with the focus upon the...

Students research Babylonian mathematics. They calculate simple surd numbers. Students find the fractional form of rational numbers expressed as decimals. They work with numbers in base 60.

Demonstrates solutions to problems #4-6 of California Geometry released state test questions. Problems address understanding of proof by contradiction and proving triangles congruent. [11:56]

Examples of proof by contradiction.

Students explore how to do a geometric proof by contradiction.

Proof by contradiction that if two lines cut by a transversal create congruent corresponding angles then the lines are parallel. [5:18]

Video defining an orthonormal set as a set of vectors that all have the length of 1 and are orthogonal to each other. Using proof by contradiction, the set is proven to be linearly independent and can be considered an orthonormal basis....

This Oswego City School District Regents Exam Prep site shows you how to proof something by showing that it is false. This look at indirect proofs includes a practice and a teacher resource page, which features a warm-up activity.

This is a site which links to specific techniques of proving including conditional statements, proof by contradiction, mathematical induction, parity arguments, and the pigeonhole principle. The site contains a link to various example...

Explore this course in logic, sets, and proof including topics of axioms, set theory, and proof by contradiction and induction.

Proof by contradiction that corresponding angle equivalence implies parallel lines.

A proof to show that the square root of two is an irrational number, followed by a shorter and even more beautiful proof.

Use this site to explore an excellent discussion of indirect proofs. The site explains in detail why such a method works as a proof and gives steps to obtain such a proof.

[Free Registration/Login may be required to access all resource tools.] This concept teaches students how to write an indirect proof and provides examples of indirect proofs in Algebra and Geometry.

[Free Registration/Login may be required to access all resource tools.] Write algebraic and geometric indirect proofs.

Come see how a counter example is helpful in some proofs. The site explains what a counter example says, and then offers a proof using a counter example.