Geometry
Practice this topic
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 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.
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.
- Angles at the intersection of two lines
- Vertical angles
- Vertical angles 2
- Proof-Vertical Angles are Equal
- Angles Formed by Parallel Lines and Transversals
- CA Geometry: Deducing Angle Measures
- Parallel lines 1
- Parallel lines 2
- Corresponding angles 2
- Same side exterior angles 2
- Same side interior angles 2
- Alternate interior angles 2
- Alternate exterior angles 2
- Congruent angles
- Identifying Parallel and Perpendicular Lines
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.
- Proof - Sum of Measures of Angles in a Triangle are 180
- Triangle Angle Example 1
- Triangle Angle Example 2
- Triangle Angle Example 3
- Challenging Triangle Angle Problem
- Proof - Corresponding Angle Equivalence Implies Parallel Lines
- Finding more angles
- Angles 1
- Angles 2
- Sum of Interior Angles of a Polygon
- Angles of a polygon
- Sum of the exterior angles of convex polygon
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.