Curated OER
What are Vertical Angles?
What makes vertical angles so special? Here's a few words that might help you figure out why: intersecting lines, congruent angles, opposite, supplementary angles. Still wondering? Then watch this video for a good explanation of vertical...
Curated OER
What is a Rhombus?
A closed figure with four sides means it's a quadrilateral. Each of the different types of quadrilaterals have special properties. The instructor in this video explains the special properties of a rhombus. Parallel sides and congruent...
Curated OER
What is a Regular Polygon?
What makes a polygon a regular polygon? Does this mean there are irregular polygons? For a polygon to be classified as a regular polygon, all the sides must be congruent and all the angles must be congruent. Those are the two rules that...
Curated OER
What is a Parallelogram?
A rectangle, a rhombus, a square, a trapezoid - are any of these a parallelogram? What are the criteria that make a shape a parallelogram? It has something to do with parallel sides, congruent sides, and congruent angles. Help your young...
Curated OER
What is a Transversal?
There are two parallel lines intersected by one straight line, what's that one line called? A transversal. There are a few more things to know about transversal lines and the angles they create. What are vertical angles? Are they...
Curated OER
How Do You Find Missing Angles in an Isosceles Triangle?
Finding the missing values of two angles in an isosceles triangle is not as difficult as it sounds. But how can two out of three angle's measurements be found? Well, there are special properties about an isosceles triangle which make...
Khan Academy
Khan Academy: Geometry: Ca Geometry: Deductive Reasoning
Demonstrates solutions to problems #1-3 of California Geometry released state test questions. Problems address understanding of deductive reasoning and congruent angles created by parallel lines cut by a transversal. [10:17]
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: Find Measure of Vertical Angles
Demonstrates how to find unknown angles for two intersecting lines when some angle information is given. [3:00]
Virtual Nerd
Virtual Nerd: What Are Perpendicular Lines?
The angles formed by perpendicular lines will always be the same. Take a look at this tutorial to learn about perpendicular lines and see a special trick involving them. [5:22]
Sophia Learning
Sophia: Notation for Congruent Parts
Explore the notation used to represent congruent sides and angles in a triangle. Take a quiz to assess learning.
Khan Academy
Khan Academy: Triangles: Wrong Statements in Proofs Example 1
A video analyzing how to recognize wrong statements in a proof. [2:48]
Virtual Nerd
Virtual Nerd: Find Missing Angles in an Isosceles Triangle Using Right Triangles
Discover how identifying your triangle first can be very helpful in solving for a missing interior angle measurement. [3:40]
Virtual Nerd
Virtual Nerd: How Do You Find a Value for X That Makes Two Lines Parallel?
This tutorial shows you how to find x so two lines are parallel. [2:47]
Khan Academy
Khan Academy: Geometry: Deductive Reasoning
This video explains what is deductive reasoning.
Study Pug
Study Pug: Perpendicular Line Proofs
Video lesson explains angles, lines, and transversals. [9:33]
Khan Academy
Khan Academy: Proving Angles Are Congruent
Sal proves that two angles are congruent in a really interesting triangle like figure.
Sophia Learning
Sophia: Angle of Depression
The concept of an angle of depression is discussed here.
Sophia Learning
Sophia: Angle of Depression: Lesson 2
The concept of an angle of depression is discussed here. This lesson is 2 of 5 in the series titled "Angle of Depression."
Sophia Learning
Sophia: Angle of Depression: Lesson 3
The concept of an angle of depression is discussed here. This lesson is 3 of 5 in the series titled "Angle of Depression."
Loyola University Chicago
Math Flix: Congruent Angles
This QuickTime movie provides an opportunity to learn about congruent/vertical angles. As you watch and listen to the teacher and student interact it helps clarify the thinking behind applying this concept.