Parallel Lines
Links and useful resources
- gr7's Prealgebra Course Outline START HERE<<<
- AoPS Online Textbook
- IXL Grade 7 index
- IXL Grade 8 index
- AoPS Alcumus
- IXL prealgebra practice index
- OpenSTAX Prealgebra-1 textbook
Concept summary and lesson
- A line crossing parallel lines makes equal corresponding angles.
- parallel lines are lines that are not in the same place and will never cross.
Worked examples
Parallel lines are lines in the same plane that will never cross. When another line crosses parallel lines, you get a lot of equal angles. The easiest way to think about this is with the vertical angle theorem we proved last time - the angles on opposite sides of the crossing point of two crossing lines are equal. With parallel lines, all of the crossing points are the same! That means that angles in corresponding positions on any of the intersections are all equal. This is true no matter how many parallel lines you have.
Useful trick
When you're dealing with problems involving angles and lines, adding extra parallel lines is often helpful in order to see the relationships more clearly, because it will immediately tell you what all of the angles are for corresponding intersections.
Media resources
- Youtube search for "A line crossing parallel lines makes equal corresponding angles."
- Youtube search for "parallel lines are lines that are not in the same place and will never cross."
Guided practice
