### Has somebody told you that parallel lines are those that never touch? Is this accurate? What about two lines in different planes that never touch? Are they parallel for that reason? What are perpendicular lines? How do I determine that lines are parallel, or perpendicular in the coordinate plane? What is the difference between the slope formula method, and the run vs. the rise method?

### In this particular lesson, you will be able to see the differences, and similarities in the above cases in question. You will get a visual display of the slope methods, and of the conditions of perpendicularity, or parallelism. You will really become an expert in the slope uses! Don't miss the opportunity to take advantage of interacting with the lesson solving the suggested problems using your stylus and the marker tools menu.

** Lesson's Content **

** Lesson's Glossary **

**Parallel lines **

Two or more coplanar lines that never cross or intersect.

**Parallel planes **

Planes that have no points in common.

**Perpendicular lines **

Two segments, rays, or lines that form a 90 degree angle.

**Perpendicular planes **

Planes in which any two intersecting lines, one in each plane, form a right angle.

**Skew lines **

Non-coplanar lines that don't intersect.

**Slope **

The measure of the tilt of a line; rise over run.

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