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# Perpendicular Lines? Definition, Properties

## What are Perpendicular Lines?

Perpendicular lines are lines that intersect at a 90-degree angle, forming a right angle. When two lines are perpendicular, they create four right angles where they meet. Perpendicular lines are found in many places, including in geometry, architecture, and engineering.

## How to Identify Perpendicular Lines?

To identify perpendicular lines, you need to look at the angles formed where the lines intersect. If the angles are 90 degrees, then the lines are perpendicular. You can also look at the slopes of the lines. If the slopes are negative reciprocals of each other, then the lines are perpendicular.

## Equation of Perpendicular Lines

The equation of a line is typically written in slope-intercept form, y = mx + b, where m is the slope of the line and b is the y-intercept. To find the equation of a line that is perpendicular to another line, you need to find the negative reciprocal of the slope of the first line. The negative reciprocal of a number is the number flipped and multiplied by -1. For example, the negative reciprocal of 2 is -1/2.

## How to Draw Perpendicular Lines?

Here are the steps to draw perpendicular lines:

1. Choose a point on a piece of paper or a drawing surface where you want the perpendicular lines to intersect.
2. Draw a horizontal line through the point. You can use a ruler or a straight edge to make sure the line is perfectly horizontal.
3. Draw a vertical line through the same point. Again, you can use a ruler or a straight edge to make sure the line is perfectly vertical.
4. Where the two lines intersect, you have a right angle, and the lines are perpendicular. 5. If you need to draw additional perpendicular lines, repeat the process by choosing a new point and drawing a horizontal and vertical line through that point.

It’s important to remember that perpendicular lines always intersect at a right angle. This means that the angle formed by the intersection of the two lines should measure exactly 90 degrees. If the angle is not exactly 90 degrees, the lines are not perpendicular.

### Examples of Perpendicular Lines

Two examples of perpendicular lines are the x-axis and the y-axis on the coordinate plane. The x-axis has a slope of 0, and the y-axis has an undefined slope. When the x-axis and y-axis intersect at the origin, they form four right angles, making them perpendicular.

Another example of perpendicular lines is a building that has walls that meet at right angles. Architects and engineers use perpendicular lines to ensure that their designs are structurally sound.

## Difference Between Parallel and Perpendicular Lines

Feature Parallel Lines Perpendicular Lines
Intersection Never intersect Intersect at a 90-degree angle
Slopes Have the same slope Have slopes that are negative reciprocals of each other
Angle Always the same Always a right angle
Distance Stay the same distance apart Have varying distances between them
Equations Have the form y = mx + b, where m is the slope Have the form y = (-1/m)x + b, where m is the slope

## FAQs on Perpendicular Line

1. What is a perpendicular line?

A perpendicular line is a line that intersects another line at a 90-degree angle, forming four right angles where they meet.

2. How do you know if two lines are perpendicular?

Two lines are perpendicular if they intersect at a right angle. You can also check if the slopes of the lines are negative reciprocals of each other.

3. How do you find the equation of a perpendicular line?

To find the equation of a line that is perpendicular to another line, you need to find the negative reciprocal of the slope of the first line. The negative reciprocal of a number is the number flipped and multiplied by -1.

4. Can two lines be perpendicular if they are not on the same plane?

No, two lines cannot be perpendicular if they are not on the same plane. Perpendicular lines must intersect at a 90-degree angle in the same plane.

5. Why are perpendicular lines important?

Perpendicular lines are important in geometry and have many practical applications in real life. They are used in architecture and engineering to ensure structural soundness in buildings and structures. They also play a role in navigation, surveying, and mapmaking.

6. What is the difference between parallel and perpendicular lines?

Parallel lines are lines that never intersect and have the same slope, while perpendicular lines intersect at a right angle and have slopes that are negative reciprocals of each other.

7. Can two perpendicular lines have the same slope?

No, two perpendicular lines cannot have the same slope. The slopes of perpendicular lines must be negative reciprocals of each other.