Khan Academy
Khan Academy: Geometry: Acute, Obtuse, and Right Angles
Demonstrates how to find all acute, obtuse, and right angles in a given diagram. [6:35]
Virtual Nerd
Virtual Nerd: How Do You Find a Missing Side of a Right Triangle Using Sine?
The sine ratio is not only used to identify a ratio between two sides of a right triangle, but it can also be used to find a missing side length. This tutorial shows you how to use the sine ratio to find that missing measurement. [4:29]
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]
Virtual Nerd
Virtual Nerd: What Are Complementary Angles?
Complementary angles always add up to 90 degrees. Watch this tutorial to learn about complementary angles and see how to use this knowledge to solve a problem involving these special types of angles. [3:20]
Khan Academy
Khan Academy: Measuring Angles in Degrees
Explains what a protractor is and how it is used to measure the size of angles. Also discusses the different types of angles. [8:23]
CK-12 Foundation
Ck 12: Elem Math: Overview of Classification of Angles
[Free Registration/Login may be required to access all resource tools.] Video describing four types of angles - right, acute, obtuse and straight. [1:19]
Virtual Nerd
Virtual Nerd: What Is a Tangent Line to a Circle?
For a line to be tangent, it must have a special relationship with a circle. It can only intersect the circle at one point. Watch this tutorial for a better understanding. [3:01]
Sophia Learning
Sophia: Classifying Triangles
This video lesson describes and provides examples of right, acute, and obtuse triangles. Students can check their understanding with an assessment. [2:24]
Sophia Learning
Sophia: Slant Height of a Pyramid
This video lesson demonstrates how to use the Pythagorean Theorem to find the slant height of pyramid.
Virtual Nerd
Virtual Nerd: How Do You Find the Cosine of an Angle in a Right Triangle?
A trigonometric ratio is a ratio between two sides of a right triangle. The cosine ratio is one of these ratios. Take a look at this tutorial to see how to find the cosine of a particular angle in a right triangle. [3:22]
Sophia Learning
Sophia: Right Angle: Lesson 10
This lesson defines the phrase right angle. It is 10 of 14 in the series titled "Right Angle."
Sophia Learning
Sophia: Right Angle: Lesson 11
This lesson defines the phrase right angle. It is 11 of 14 in the series titled "Right Angle."
Sophia Learning
Sophia: Right Angle: Lesson 12
This lesson defines the phrase right angle. It is 12 of 14 in the series titled "Right Angle."
Sophia Learning
Sophia: Right Angle: Lesson 13
This lesson defines the phrase right angle. It is 13 of 14 in the series titled "Right Angle."
Sophia Learning
Sophia: Right Angle: Lesson 9
This lesson defines the phrase right angle. It is 9 of 14 in the series titled "Right Angle."
Sophia Learning
Sophia: Right Angle: Lesson 2
This lesson defines the phrase right angle. It is 2 of 14 in the series titled "Right Angle."
Sophia Learning
Sophia: Right Angle: Lesson 3
This lesson defines the phrase right angle. It is 3 of 14 in the series titled "Right Angle."
Khan Academy
Khan Academy: Recognizing Angles
Demonstrates how to solve problems that ask you to identify types of angles. [2:15]
Shmoop University
Shmoop: Angles
This video discusses angles in an original, cute manner, illustrating different types of angles with animated characters.