Proofs Teacher Resources
Find Proofs lesson plans and worksheets
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Curated OER
Angles in Polygons
In this geometry worksheet, 10th graders solve problems involving quadrilaterals using the angle sum of quadrilaterals. They solve for linear pairs, opposite angle theorem and triangular angles. There are 5 questions.
Curated OER
Logical Relationship of Postulates & Theorems
In this postulates and theorems worksheet, students explore a concept map containing information about angles and sides, alternate interior angles, and diagonals of a parallelogram. They use the concept map to prove theorems...
Curated OER
Polygons All Around Us!
Students explore the concept of polygon properties. In this polygon properties lesson plan, students draw polygons with different numbers of sides such as pentagons, octagons, hexagons, etc. Students identify different geometric shapes...
Khan Academy
Khan Academy: Geometry: Corresponding Angle Equivalence Implies Parallel Lines
Proof by contradiction that if two lines cut by a transversal create congruent corresponding angles then the lines are parallel. [5:18]
Khan Academy
Khan Academy: Geometry: Angles of Parallel Lines 2
Explains how to determine the measures of all the angles formed when parallel lines are cut by a transversal based on the measure of one angle. Explains how to use corresponding congruent angles to determine if lines cut by a transversal...
Khan Academy
Khan Academy: Parallel Lines & Corresponding Angles Proof
Proof by contradiction that corresponding angle equivalence implies parallel lines.
Khan Academy
Khan Academy: Geometry: Ca Geometry: More Proofs
Demonstrates solutions to problems #7-10 of California Geometry released state test questions. Problems address understanding of congruent angle pairs when parallel lines are cut by a transversal, counterexamples, and properties of the...
Khan Academy
Khan Academy: Geometry: Proof Sum of Measures of Angles in a Triangle Are 180
Proof that the sum of the angles in a triangle is 180 using the relationship of angles formed when parallel lines are cut by a transversal. This video also appears in the Geometry: Triangles strand. [6:31]
Texas Instruments
Texas Instruments: Angle Sum in Triangles Proof: Rotation and a Parallel Line
This investigation uses Cabri Jr. and a cleaver rotation of a triangle to "prove" that the angles in a triangle add up to 180. This could be used to reinforce triangles and paralled lines as well as introduce the concept of rotating an...
Khan Academy
Khan Academy: Geometry: Proof: Opposite Angles of Parallelogram Congruent
This video tutorial demonstrates how to prove that the opposite angles of a parallelogram are congruent based on knowledge of the special angles created when parallel lines are cut by a transversal. [4:08]
Khan Academy
Khan Academy: Geometry: Proof: Diagonals of Parallelogram Bisect Each Other
Demonstrates how to prove that the diagonals of a parallelogram bisect each other based on knowledge of the special angles created when parallel lines are cut by a transversal and the triangle congruency postulates. [9:06]
Khan Academy
Khan Academy: Geometry: Proof: Opposite Sides of Parallelogram Congruent
Demonstrates how to prove that the opposite sides of a parallelogram are congruent based on knowledge of the special angles created when parallel lines are cut by a transversal and the triangle congruency postulates. [8:30]
Study Pug
Study Pug: Perpendicular Line Proofs
Video lesson explains angles, lines, and transversals. [9:33]
Khan Academy
Khan Academy: Geometry: Ca Geometry: Pythagorean Theorem, Compass Constructions
This video tutorial demonstrates solutions to problems #51-55 of the California Geometry released state test questions. Problems address proving and using the Pythagorean theorem and compass constructions. [12:35]