Khan Academy on a Stick
Angles and intersecting lines
This topic continues our journey through the world of Euclid by helping us understand angles and how they can relate to each other.

Angle basics
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Definition of an angle. How to denote an angle using points on the angle (including the vertex)

Measuring angles in degrees
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How to measure an angle in degrees

Using a protractor
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Acute right and obtuse angles
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The difference between acute, obtuse and right angles
 Vertical, adjacent and linearly paired angles
Angle basics and measurement
This tutorial will define what an angle is and help us think about how to measure them. If you're new to angles, this is a great place to start.

Introduction to vertical angles
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Figuring out angles at the intersection of two lines
 Using algebra to find the measures of vertical angles

ProofVertical Angles are Equal
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Proving that vertical angles are equal

Angles Formed by Parallel Lines and Transversals
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Parallel lines, transversal lines, corresponding angles

Identifying Parallel and Perpendicular Lines
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Identifying Parallel and Perpendicular Lines
 Figuring out angles between transversal and parallel lines
 Using algebra to find measures of angles formed from transversal

CA Geometry: Deducing Angle Measures
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4650, deducing the measure of angles
Angles between intersecting and parallel lines
Welcome. I'd like to introduce you to Mr. Angle. Nice to meet you. So nice to meet you. This tutorial introduces us to angles. It includes how we measure them, how angles relate to each other and properties of angles created from various types of intersecting lines. Mr. Angle is actually far more fun than you might initially presume him to be.

Proof  Sum of Measures of Angles in a Triangle are 180
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Proof that the sum of the measures of the angles in a triangle are 180

Triangle Angle Example 1
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Figuring out angles in a triangle. A little about exterior angles being the sum of the remote interior angles

Triangle Angle Example 2
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Another example finding angles in triangles

Triangle Angle Example 3
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Multiple ways to solve for the angles of multiple triangles

Challenging Triangle Angle Problem
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Interesting problem finding the sums of particular exterior angles of an irregular pentagon

Proof  Corresponding Angle Equivalence Implies Parallel Lines
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Proof by contradiction that corresponding angle equivalence implies parallel lines

Finding more angles
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Example of angle hunting!

Sum of Interior Angles of a Polygon
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Showing a generalized way to find the sum of the interior angles of any polygon

Sum of the exterior angles of convex polygon
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More elegant way to find the sum of the exterior angles of a convex polygon
Angles with triangles and polygons
Do the angles in a triangle always add up to the same thing? Would I ask it if they didn't? What do we know about the angles of a triangle if two of the sides are congruent (an isosceles triangle) or all three are congruent (an equilateral)? This tutorial is the place to find out.

Introduction to angles (old)
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What an angle is. Angles in a circle. Complementary and supplementary angles.

Angles (part 2)
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More on complementary and supplementary angles. Introduction to opposite angles.

Angles (part 3)
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Angles formed when a transversal intersects parallel lines.

Angles formed between transversals and parallel lines
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Angles of parallel lines

Angles of parallel lines 2
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Angles of parallel lines examples

The Angle Game
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Using what we know to solve for angles in the Angle Game.

Angle Game (part 2)
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More examples of the Angle Game.

Acute right and obtuse angles
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The difference between acute, obtuse and right angles
Sal's old angle videos
These are some of the classic, original angle video that Sal had done way back when (like 2007). Other tutorials are more polished than this one, but this one has charm. Also not bad if you're looking for more examples of angles between intersected lines, transversals and parallel lines.

Complementary and supplementary angles
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Basics of complementary, supplementary, adjacent and straight angles. Also touching on what it means to be perpendicular
 Example using algebra to find measure of complementary angles
 Example using algebra to find measure of supplementary angles
Complementary and supplementary angles
In this tutorial we'll look at the most famous types of anglepairscomplementary and supplementary angles. This aren't particularly deep concepts, but you'll find they do come in handy!