Instructional Video12:08
Khan Academy

Part 2 of Proof of Heron's Formula, Perimeter, Area, and Volume, Geometry

For Students 9th - 12th
Picking up where the prior installment in the series on HeronÕs formula ended, Sal provides a more detailed explanation.
Instructional Video3:53
Corbett Maths

Coordinates and Shapes

For Students 6th - 11th Standards
Where is the point? Given three points on the coordinate plane, the video walks through the steps to find the location of the fourth point to create a given special quadrilateral. The narrator first determines the coordinates of the...
Instructional Video3:58
Brightstorm

Triangle Angle Sum

For Students 9th - 12th Standards
Don't believe everything that you hear — make them prove it! The video shows two methods to prove the Triangle Angle Sum Theorem. The following two videos apply the theorem to finding missing angle measures.
Instructional Video14:29
2
2
Flipped Math

Addition Postulate

For Students 9th - 12th Standards
Add a little algebra to the geometry. Class members learn about the Addition Postulate for segments and angles. The pupils use their knowledge of solving equations to find lengths of segments and measures of angles. Individuals apply...
Instructional Video2:05
Curated OER

What's a Venn Diagram, and How Do You Find the Intersection and Union of a Set?

For Teachers 6th - 8th
A straightforward illustration of a Venn diagram. Intersection is what the sets have in common, and the union is all the elements of the sets. The diagram certainly helps you see what this means.
Instructional Video3:48
Khan Academy

Parallel Lines From Equation, Mathematics I, High School Math

For Students 7th - 9th
Here is a fairly basic video that uses three equations, each written in slope-intercept form, to determine whether the lines are parallel. Sal graphs each equation on the same coordinate plane to show how their slopes compare. The video...
Instructional Video
Sophia Learning

Sophia: Types of Proofs

For Students 9th - 10th Standards
Explore the similarities and differences between paragraph proofs, flow chart proofs, and two-column proofs. Assess learning with a quiz.
Instructional Video
Sophia Learning

Sophia: Introduction to Geometric Proof

For Students 9th - 10th Standards
Explore the structure and how to complete a flow proof and a two-column proof.
Instructional Video
Sophia Learning

Sophia: Intermediate Proof

For Students 9th - 10th Standards
Use the two-column proof and the flow proof to prove two triangles congruent.
Instructional Video
Khan Academy

Khan Academy: Triangles: Another Pythagorean Theorem Proof

For Students 9th - 10th Standards
Students explore the Pythagorean Theorem by exploring a visual proof of the Theorem as they watch a video tutorial.
Instructional Video
Khan Academy

Khan Academy: Geometry: Ca Geometry: Proof by Contradiction

For Students 9th - 10th Standards
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]
Instructional Video
Khan Academy

Khan Academy: Geometry: Proof Sum of Measures of Angles in a Triangle Are 180

For Students 9th - 10th
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]
Instructional Video
Khan Academy

Khan Academy: Geometry: Ca Geometry: More Proofs

For Students 9th - 10th Standards
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...
Instructional Video
Khan Academy

Khan Academy: Geometry: Equilateral Triangle Sides and Angles Congruent

For Students 9th - 10th Standards
In this video tutorial [6:29], the instructor models a proof so show that if the sides of an equilateral triangle are congruent, then all the angles are congruent and vice versa. The instructor uses the knowledge of congruent legs and...
Instructional Video
Khan Academy

Khan Academy: Geometry: Two Column Proof Showing Segments Are Perpendicular

For Students 9th - 10th Standards
In this video tutorial [11:06], the instructor shows how to construct a two-column proof using triangle congruence postulates to prove that two line segments are perpendicular.
Instructional Video
Khan Academy

Khan Academy: Geometry: 30 60 90 Triangle Side Ratios Proof

For Students 9th - 10th
In this video tutorial [6:59], the instructor provides a proof for the relationship among the legs and hypotenuse of 30-60-90 triangles by breaking an equilateral triangle into two congruent triangles and using the Pythagorean threorem.
Instructional Video
Khan Academy

Khan Academy: Geometry: Triangle Medians and Centroids (2 D Proof)

For Students 9th - 10th
This video tutorial [15:15] provides a two-dimensional proof that the centroid is located two-thirds the way along every median of a triangle. This is a follow up to the proof in three-dimensions provided in the video, "Triangle Median...
Instructional Video
Khan Academy

Khan Academy: Geometry: Congruent Triangle Proof Example

For Students 9th - 10th Standards
Demonstrates how to use triangle congruency to prove that a given point is the midpoint of a given line segment. The proof is written in the form of a two-column proof. Practice problems available. [5:46]
Instructional Video
Khan Academy

Khan Academy: Geometry: Congruent Parts of Iscosceles Triangles

For Students 9th - 10th Standards
Proof that if the legs of an isosceles triangle are congruent then the base angles are congruent and vice versa using triangle congruency postulates. The proof is written as a two-column proof. [9:03]
Instructional Video
Khan Academy

Khan Academy: Geometry: Circumcenter of a Triangle

For Students 9th - 10th Standards
Explains using multiple proofs that a point on a perpendicular bisector is equidistant from the endpoints of the segment it bisects. Proofs use triangle congruency postulates. Lays the foundation for understanding the circumcenter of a...
Instructional Video
Khan Academy

Khan Academy: Geometry: Right Triangles Inscribed in Circles (Proof)

For Students 9th - 10th Standards
This video tutorial [5:35] explains that if the diameter of a circle is one of the sides of a triangle inscribed in the circle then the triangle is a right triangle. This video also appears in the strand Geometry: Circles.
Instructional Video
Khan Academy

Khan Academy: Geometry: Ca Geometry: Pythagorean Theorem, Compass Constructions

For Students 9th - 10th Standards
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]
Instructional Video
Khan Academy

Khan Academy: Geometry: Corresponding Angle Equivalence Implies Parallel Lines

For Students 9th - 10th Standards
Proof by contradiction that if two lines cut by a transversal create congruent corresponding angles then the lines are parallel. [5:18]
Instructional Video
Khan Academy

Khan Academy: Geometry: Angle Bisector Theorem Proof

For Students 9th - 10th Standards
Explanation and proof of angle bisector theorem. [8:35]

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