Instructional Video
Khan Academy

Khan Academy: Geometry: Sum of the Exterior Angles of Convex Polygon

For Students 9th - 10th
Demonstrates how to determine that the exterior angle sum of a convex polygon is 360 degrees. Practice problems available. [5:24]
Instructional Video
Khan Academy

Khan Academy: Geometry: Proof Vertical Angles Are Equal

For Students 9th - 10th Standards
Proof that the measures of vertical angles are equal based on properties of supplementary angles. [4:51]
Instructional Video
Khan Academy

Khan Academy: Geometry: Language and Notation of the Circle

For Students 9th - 10th Standards
Formally defines a circle and different parts of a circle. Identifies the proper notation for naming different parts of a circle. [11:12]
Instructional Video
Khan Academy

Khan Academy: Geometry: Similarity Postulates

For Students 9th - 10th Standards
Explains the minimum amount of information needed to determine if two triangles are similar. Names and illustrates the similarity postulates: AA, SSS, and SAS. [12:14]
Instructional Video
Khan Academy

Khan Academy: Geometry: Equilateral and Isosceles Example Problems

For Students 9th - 10th
Demonstrates how to use the triangle sum theorem, properties of equilateral and isosceles triangles, and special angle pairs to determine the unknown measures of angles in three different diagrams. [6:27]
Instructional Video
Khan Academy

Khan Academy: Geometry: The Pythagorean Theorem

For Students 9th - 10th
This video tutorial is n introduction to the Pythagorean theorem. The instructor explains how to use the Pythagorean theorem to find the length of the hypotenuse or the length of one of the legs. At the end of the video, practice...
Instructional Video
Khan Academy

Khan Academy: Geometry: Example Involving Isosceles Triangle and Parallel Lines

For Students 9th - 10th Standards
Demonstrates how to use the triangle sum theorem, properties of isosceles triangles, and special angle pairs formed when parallel lines are cut by a transversal to set up an equation using given algebraic expressions for angle measures...
Instructional Video
Khan Academy

Khan Academy: Geometry: Angles at the Intersection of Two Lines

For Students 9th - 10th Standards
Explains how to determine the measures of angles formed by interecting lines when given the measure of one angle. [7:19]
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: Other Triangle Congruence Postulates

For Students 9th - 10th Standards
In this video tutorial [13:28], the instructor identifies the different triangle congruency postulates: SSS, SAS, ASA, AAS. Practice problems available.
Instructional Video
Khan Academy

Khan Academy: Geometry: Challenging Triangle Angle Problem

For Students 9th - 10th
Demonstrates how to find the sum of the exterior angles of an irregular pentagon by breaking the pentagon into three triangles and using the triangle sum theorem. [8:37]
Instructional Video
Khan Academy

Khan Academy: Geometry: Similar Triangle Basics

For Students 9th - 10th Standards
Explains the difference between congruent triangles and similar triangles. Introduces the idea of scale factors. [9:17]
Instructional Video
Khan Academy

Khan Academy: Geometry: Another Isosceles Example Problem

For Students 9th - 10th
Explains how to use given algebraic expressions for the measures of angles in an isosceles triangle and apply knowledge of the triangle sum theorem and the knowledge that the base angles of an isosceles triangle are congruent to...
Instructional Video
Khan Academy

Khan Academy: Geometry: Congruent Triangles and Sss

For Students 9th - 10th Standards
In this video tutorial [11:29], the instructor explains how to use triangle congruence to identify measures of corresponding sides and angles in triangles. Defines side-side-side (SSS) postulate. Practice problems available.
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: Area of a Regular Hexagon

For Students 9th - 10th
This video [7:50] demonstrates how to determine the area a regular hexagon with side length of 2 sq. rt. 3 based on knowledge of 30-60-90 triangles and the area formula of a triangle.
Instructional Video
Khan Academy

Khan Academy: Geometry: Inscribed and Central Angles

For Students 9th - 10th Standards
Proof that the measure of an inscribed angle is half the measure of a central angle when the angles intercept the same arc. [14:16]
Instructional Video
Khan Academy

Khan Academy: Geometry: Congruent Triangle Example 2

For Students 9th - 10th Standards
Demonstrates how to use triangle congruency to prove that corresponding sides of congruent triangles are congruent and then identifies other congruent parts in the overlapping triangle diagram. The proof is written in the form of a...
Instructional Video
Khan Academy

Khan Academy: Geometry: Medians Divide Into Smaller Triangles of Equal Area

For Students 9th - 10th
This video tutorial [7:46] demonstrates that the three medians of a triangle divide it into six smaller triangles with equal areas.
Instructional Video
Khan Academy

Khan Academy: Right Triangle Geometry Basic Example

For Students 9th - 10th
The video from Khan Academy provides practice questions for the SAT. Students will watch Sal work through a basic right triangle trigonometry problem.
Instructional Video
Khan Academy

Khan Academy: Right Triangle Geometry Harder Example

For Students 9th - 10th
The video from Khan Academy provides practice questions for the SAT. Students will watch Sal work through a harder right triangle trigonometry problem.
Instructional Video
Khan Academy

Khan Academy: Terms & Labels in Geometry

For Students 3rd - 4th Standards
Learn about geometry terms like point, line, and ray. We will also learn how to label them.
Instructional Video
Math Planet

Math Planet: Geometry: Triangles

For Students 9th - 10th Standards
Discussion of triangles through the use of examples and a video lesson. [1:08]
Instructional Video
Loyola University Chicago

Math Flix: Similar Figures: Proof Using Proportions

For Students 9th - 10th Standards
This QuickTime movie provides an opportunity to develop the basic geometric term, similar, by checking to see if figures are proportionaly similar. As you watch and listen to the teacher and student interact it helps clarify the thinking...

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