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.
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Angle basics
The naming of an angle is related to the line segments that create it. We'll also learn about the angle's vertex. Come on. Let's do this.
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Measuring angles in degrees
Let's come up with an exact way to measure an angle using a protractor. We'll also lean about acute angles. Not to be confused with augly angles :)
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Measuring angles using a protractor
Let's use our virtual protractor to measure some angles together, shall we?
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More angle measurements using a protractor
We're practicing measuring angles using the virtual protractor. Do this a few times with us and you'll use a real protractor like a pro!
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Acute right and obtuse angles
We briefly discussed the types of angles in the last tutorial but we'll delve a little deeper into acute, obtuse, and right angles here.
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Vertical, adjacent and linearly paired angles
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Angle measurement and circle arcs
Did you know that the measurement of an angle is realted to the arc of a circle? Yes, indeed! Watch.
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Angles and circumference
We're slowly starting to put things together in this example exercise: angle, circle, circumference, and fractions. Woohoo!
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.
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Introduction to vertical angles
By using our knowledge of supplementary, adjacent, and vertical angles, we can solve problems involving the intersection of two lines. Including this one!
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Find measure of vertical angles
Now that we've learned about complementary and supplementary angles, let's use algebra to find the measure of vertical angles, or angles opposite each other when two lines cross.
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Proof: Vertical angles are equal
Proving that vertical angles are equal
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Angles formed by parallel lines and transversals
Parallel lines, transversal lines, corresponding angles
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Identifying parallel and perpendicular lines
Let's now apply what we learned and do an exercise together in which we identify parallel and perpendicular lines.This is great practice.
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Figuring out angles between transversal and parallel lines
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Using algebra to find measures of angles formed from transversal
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CA Geometry: Deducing angle measures
46-50, 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.
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Proof: Sum of measures of angles in a triangle are 180
Proof that the sum of the measures of the angles in a triangle are 180
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Triangle angle example 1
Figuring out angles in a triangle. A little about exterior angles being the sum of the remote interior angles
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Triangle angle example 2
Another example finding angles in triangles
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Triangle angle example 3
Multiple ways to solve for the angles of multiple triangles
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Challenging triangle angle problem
Interesting problem finding the sums of particular exterior angles of an irregular pentagon
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Proof: Corresponding angle equivalence implies parallel lines
Proof by contradiction that corresponding angle equivalence implies parallel lines
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Finding more angles
Example of angle hunting!
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Sum of interior angles of a polygon
Showing a generalized way to find the sum of the interior angles of any polygon
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Sum of the exterior angles of convex polygon
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.
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Introduction to angles (old)
What an angle is. Angles in a circle. Complementary and supplementary angles.
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Angles (part 2)
More on complementary and supplementary angles. Introduction to opposite angles.
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Angles (part 3)
Angles formed when a transversal intersects parallel lines.
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Angles formed between transversals and parallel lines
Angles of parallel lines
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Angles of parallel lines 2
Angles of parallel lines examples
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The angle game
Using what we know to solve for angles in the Angle Game.
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Angle game (part 2)
More examples of the Angle Game.
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Acute right and obtuse angles
We briefly discussed the types of angles in the last tutorial but we'll delve a little deeper into acute, obtuse, and right angles here.
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.
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Complementary and supplementary angles
Let's add some tools to our geometry tool belt. Here's a thorough explanation of complementary and supplementary angles, as well as definitions of adjacent and straight angles.
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Find measure of complementary angles
In this example, let's put some Algebra to work to find the measure of two angles whose sum equals 90 degrees, better knows as complementary angles.
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Find measure of supplementary angles
Watch and understand how to find the measure of two angles whose sum is 180 degrees, or supplementary angles.
Complementary and supplementary angles
In this tutorial we'll look at the most famous types of angle-pairs--complementary and supplementary angles. This aren't particularly deep concepts, but you'll find they do come in handy!