Intermediate Geometry : How to find out if lines are perpendicular

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

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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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