Intermediate Geometry : Perpendicular Lines

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

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Example Question #8 : How To Find Out If Lines Are Perpendicular

Are the lines of the equations 

and

parallel, perpendicular, or neither?

Possible Answers:

Perpendicular

Parallel

Neither

Correct answer:

Neither

Explanation:

Write each equation in the slope-intercept form  by solving for ; the -coefficient  is the slope of the line.

Subtract  from both sides:

The line of this equation has slope .

 

Subtract  from both sides:

Multiply both sides by 

The line of this equation has slope .

Two lines are parallel if and only if they have the same slope; this is not the case. They are perpendicular if and only if the product of their slopes is ; this is not the case, since

.

The correct response is that the lines are neither parallel nor perpendicular.

Example Question #9 : How To Find Out If Lines Are Perpendicular

Are the lines of the equations 

and

parallel, perpendicular, or neither? 

Possible Answers:

Parallel 

Perpendicular

Neither

Correct answer:

Neither

Explanation:

Write each equation in the slope-intercept form  by solving for ; the -coefficient  is the slope of the line.

Subtract  from both sides:

Multiply both sides by :

The slope is the -coefficient 

 

Add  to both sides:

Multiply both sides by :

The slope is the -coefficient .

Two lines are parallel if and only if they have the same slope; this is not the case. They are perpendicular if and only if the product of their slopes is ; this is not the case, since . The lines are neither parallel nor perpendicular.

Example Question #1 : How To Find Out If Lines Are Perpendicular

The slopes of two lines on the coordinate plane are  and 4. 

True or false: the lines are perpendicular.

Possible Answers:

True

False

Correct answer:

True

Explanation:

Two lines on the coordinate plane are perpendicular if and only if the product of their slopes is . The product of the slopes of the lines in question is

,

so the lines are indeed perpendicular.

Example Question #11 : How To Find Out If Lines Are Perpendicular

Two lines intersect at the point . One line passes through the point ; the other passes through .

True or false: The lines are perpendicular.

Possible Answers:

True

False

Correct answer:

False

Explanation:

Two lines are perpendicular if and only if the product of their slopes is . The slope of each line can be found from the coordinates of two points using the slope formula

To find the slope of the first line, set :

To find the slope of the second line, set :

The product of the slopes is

As the product is not , the lines are not perpendicular.

Example Question #171 : Coordinate Geometry

The slopes of two lines are 6 and . True or false: the lines are perpendicular. 

Possible Answers:

False

True

Correct answer:

False

Explanation:

Two lines on the coordinate plane are perpendicular if and only if the product of their slopes is . The product of the slopes of the lines in question is

The product is not equal to , so the lines are not perpendicular.

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