en.wikipedia.org/wiki/Perpendicular

If two **lines** (a and b) are both **perpendicular** to a third **line** (c), all of the angles
formed along the third **line** are right ...

www.coolmath.com/algebra/08-lines/14-perpendicular-lines-01

These **lines** are **perpendicular**. (They form a 90 degree angle.) So, what's going
on with the slopes? m1 = 2 and m2 = -1 / 2. Notice that they are inverses

www.khanacademy.org/math/basic-geo/basic-geo-lines/parallel-perp/a/parallel-perpendicular-review

Review the basics of parallel and **perpendicular lines**. Identify and draw parallel
and **perpendicular lines** in some practice problems.

www.khanacademy.org/math/geometry/hs-geo-analytic-geometry/hs-geo-parallel-perpendicular-eq/v/perpendicular-lines

Sal determines which pairs out of a few given linear equations are **perpendicular**.

www.khanacademy.org/math/basic-geo/basic-geo-lines/parallel-perp/v/parallel-and-perpendicular-lines-intro

Parallel lines never intersect, and **perpendicular lines** intersect at a 90 degree
angle. Learn how to identify parallel and **perpendicular lines**.

www.mathsisfun.com/definitions/perpendicular-lines.html

**Perpendicular Lines**. more ... **Perpendicular Lines**. Lines that are at right angles (
90°) to each other. Try for yourself: See: Parallel Lines. Next.

www.mathsisfun.com/perpendicular-parallel.html

**Perpendicular** and Parallel. **Perpendicular**. It just means at right angles (90°) to.
The red **line** is **perpendicular** to the blue **line** in each of these examples:.

www.purplemath.com/modules/slope3.htm

Demonstrates how to determine if slopes are for parallel lines, **perpendicular**
**lines**, or neither. Explains why graphing is not generally helpful for this type of ...

virtualnerd.com/geometry/fundamentals/angle-pair-relationships/perpendicular-lines-definition

Note: **Perpendicular lines** have a special property. The angles formed by
**perpendicular lines** will always be the same. Check out this tutorial to learn about
...