Khan Academy
Khan Academy: Geometry: 30 60 90 Triangle Example Problem
In this video tutorial [6:40], the instructor explains how to apply the relationships of the sides of a 30-60-90 triangle to solve a perimeter problem involving a rectangle that has had one of the angles trisected.
Khan Academy
Khan Academy: Geometry: Triangle Medians and Centroids
This video tutorial [8:59] reviews the definitions of median and centroid in relation to a triangle and proves that the centroid is two-thirds the way along a median. The proof is done be drawing a triangle in three-dimensions.
Khan Academy
Khan Academy: Geometry: Cylinder Volume and Surface Area
Explains how to calculate surface area and volume of a cylinder. Practice problems available. [8:07]
Khan Academy
Khan Academy: Geometry: Median Centroid Right Triangle Example
This video tutorial [9:00]explains how to find various measures of triangles formed by the medians of a right triangle. Based on the properties of the medians of a triangle, properties of centroids, and the Pythagorean theorem.
Khan Academy
Khan Academy: Geometry: Sum of Interior Angles of a Polygon
Demonstrates how to generalize the formula for finding the interior angle sum of a polygon by noticing how many non-overlapping triangles a polygon can be broken into. Practice problems available. [9:10]
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Khan Academy: Geometry: Congruent Triangle Proof Example
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]
Khan Academy
Khan Academy: Geometry: Introduction to the Pythagorean Theorem
This video tutorial [8:35] identifies the parts of a right triangle and demonstrates how to use the Pythagorean Theorem to determine an unknown side length of a right triangle.
Khan Academy
Khan Academy: Geometry: Area of a Parallelogram
Demonstrates how to derive the formula for the area of parallelogram based on the area formula for a triangle. [5:42]
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Khan Academy: Geometry: Area of Inscribed Equilateral Triangle (Basic Trig Used)
Demonstrates how to find the area of an equilateral triangle inscribed in a circle by applying the area formula for a circle and Heron's formula. Some basic trigonometry (SOHCAHTOA) is also used. [11:38]
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Khan Academy: Geometry: Circumcenter of a Right Triangle
Proves that the circumcenter of a right triangle is the midpoint of the hypotenuse. [5:42]
Khan Academy
Khan Academy: Geometry: Sum of the Exterior Angles of Convex Polygon
Demonstrates how to determine that the exterior angle sum of a convex polygon is 360 degrees. Practice problems available. [5:24]
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Khan Academy: Geometry: Proof Vertical Angles Are Equal
Proof that the measures of vertical angles are equal based on properties of supplementary angles. [4:51]
Khan Academy
Khan Academy: Geometry: Language and Notation of the Circle
Formally defines a circle and different parts of a circle. Identifies the proper notation for naming different parts of a circle. [11:12]
Khan Academy
Khan Academy: Geometry: Similarity Postulates
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]
Khan Academy
Khan Academy: Geometry: Equilateral and Isosceles Example Problems
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]
Khan Academy
Khan Academy: Geometry: The Pythagorean Theorem
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...
Khan Academy
Khan Academy: Geometry: Example Involving Isosceles Triangle and Parallel Lines
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...
Khan Academy
Khan Academy: Geometry: Angles at the Intersection of Two Lines
Explains how to determine the measures of angles formed by interecting lines when given the measure of one angle. [7:19]
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Khan Academy: Geometry: Congruent Parts of Iscosceles Triangles
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]
Khan Academy
Khan Academy: Geometry: Other Triangle Congruence Postulates
In this video tutorial [13:28], the instructor identifies the different triangle congruency postulates: SSS, SAS, ASA, AAS. Practice problems available.
Khan Academy
Khan Academy: Geometry: Challenging Triangle Angle Problem
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]
Khan Academy
Khan Academy: Geometry: Similar Triangle Basics
Explains the difference between congruent triangles and similar triangles. Introduces the idea of scale factors. [9:17]
Khan Academy
Khan Academy: Geometry: Another Isosceles Example Problem
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...
Khan Academy
Khan Academy: Geometry: Congruent Triangles and Sss
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.
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