Khan Academy
Khan Academy: Geometry: Circumcenter of a Triangle
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...
Khan Academy
Khan Academy: Algebra I Worked Examples: Perpendicular Lines 2
The learning exercise is a video that examines perpendicular lines. Students watch an example on how to write the equation of a perpendicular line. [3:01]
Khan Academy
Khan Academy: More Analytic Geometry: Perpendicular Lines 2
This video demonstrates how to find the equation of a line when given a point on the line and the equation of a line perpendicular to it.
Khan Academy
Khan Academy: Dilating Shapes: Shrinking Down a Triangle by Half
Demonstrates how to plot a triangle on a Cartesian grid after a dilation and with a scale factor of 1/2. [2:26]
Khan Academy
Khan Academy: Geometry: Lines, Line Segments, and Rays
Compares qualities of line segments, lines, and rays. Practice problems available. [3:38]
Khan Academy
Khan Academy: Geometry: Angle Bisector Theorem Examples
Explains how to use the angle bisector theorem to solve for the sides of a triangle. [3:04]
Khan Academy
Khan Academy: Angles: Angle Bisector Theorem Examples
Explanation on how to use the Angle Bisector Theorem to solve for sides of a triangle.
Khan Academy
Khan Academy: Formal Understanding of Congruence
Simple proof using RSH postulate to show that a radius perpendicular to a chord bisects it
Khan Academy
Khan Academy: Introduction to Euclidean Geometry: Identifying Rays
In this video students learn about the key aspects of rays.
Sophia Learning
Sophia: Coordinate Geometry of Parallelograms
This lesson will demonstrate how to use slope, midpoint, and distance formulas to determine from the coordinates of the vertices if a quadrilateral is a parallelogram in a coordinate plane. Students can check their understanding with an...
Khan Academy
Khan Academy: Geometry: Finding More Angles
Solving for measures of the angles in a triangle using algebra, the triangle sum theorem, and properties of angles created by a transversal that cuts parallel lines. [6:05]
Khan Academy
Khan Academy: Geometry: Identifying Parallel and Perpendicular Lines
Identifying parallel and perpendicular lines in a diagram. [3:34]
Khan Academy
Khan Academy: Geometry: Triangle Angle Example 1
Explains how to use the triangle sum theorem to solve for missing angle measures in a triangle. Also addresses the relationship between the measure of an exterior angle of a triangle and the measures of the remote interior angles. This...
Khan Academy
Khan Academy: Triangles: Median Centroid Right Triangle Example
This video demonstrates how to find various measures of triangles formed by the medians of a right triangle.
Khan Academy
Khan Academy: Triangles: Circumcenter of a Triangle
Multiple proofs showing that a point is on a perpendicular bisector of a segment if and only if it is equidistant from the endpoints. Using this to establish the circumcenter, circumradius, and circumcircle for a triangle.
Khan Academy
Khan Academy: Angles (Part 3)
Identifies and defines the types of angles formed by parallel lines cut by a transversal and the relationship of their measures.
Khan Academy
Khan Academy: Triangles: Circumcenter of a Right Triangle
The video tutorial shows that the midpoint of the hypotenuse is the circumcenter.
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: Example Involving an Isosceles Triangle and Parallel Lines
This video 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...
Khan Academy
Khan Academy: Geometry: Angles Formed Between Transversals and Parallel Lines
Explains the relationship between the measures of angles formed when parallel lines are cut by a transversal based on relationships of corresponding, vertical, and supplementary angles. [7:53]
Khan Academy
Khan Academy: Geometry: Angles (Part 3)
Identifies and defines the types of angles formed by parallel lines cut by a transversal and the relationship of their measures. Discusses Triangle Sum Theorem. [9:48]
Khan Academy
Khan Academy: Geometry: Euler's Line Proof
Proves that the circumcenter, orthocenter, and centroid all lie on the same line, the Euler line. Proof relies on understanding of properties of similar triangles and properties of special parts of a triangle. [9:50]
Khan Academy
Khan Academy: Dilations: Center
Determining the center of dilation, given a figure and its image under a dilation.
Khan Academy
Khan Academy: Dilating Lines
Sal shows how we can use dilations to map a line into another, parallel, line.