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

Let's graph these **lines**: * I'm using y = mx + b stuff to graph them!

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/a/parallel-perpendicular-review

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

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.varsitytutors.com/sat_math-help/how-to-find-the-equation-of-a-perpendicular-line

Using the slope intercept formula, we can see the slope of **line** p is ¼. Since **line** k
is **perpendicular** to **line** p it must have a slope that is the negative reciprocal.

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/algebra-1/linear-equation-analysis/parallel-perpendicular-lines/perpendicular-lines/slope-intercept-from-point-and-perpendicular-line

Want to find the slope-intercept form of a line when you're given a point on that
line and another line perpendicular to that line? Remember, **perpendicular lines**
...

virtualnerd.com/algebra-1/linear-equation-analysis/parallel-perpendicular-lines/perpendicular-lines

How Do You Write an Equation of a Line in Slope-Intercept Form If You Have
One Point and a **Perpendicular Line**? Want to find the slope-intercept form of a
line ...