Parallel and Perpendicular Lines

Front

What are parallel lines?

Back

Parallel lines are lines in a plane that never meet or intersect. They have the same slope.

Front

What are perpendicular lines?

Back

Perpendicular lines are lines that intersect at a right angle (90 degrees). The slopes of perpendicular lines are negative reciprocals of each other.

Front

If the slope of line A is 2, what is the slope of a line parallel to it?

Back

The slope of a line parallel to line A is also 2.

Front

If the slope of line B is 3, what is the slope of a line perpendicular to it?

Back

The slope of a line perpendicular to line B is -1/3.

Front

What is the slope of a horizontal line?

Back

The slope of a horizontal line is 0.

Front

What is the slope of a vertical line?

Back

The slope of a vertical line is undefined.

Front

Given the slopes of two lines, how can you determine if they are parallel?

Back

Two lines are parallel if their slopes are equal.

Front

Given the slopes of two lines, how can you determine if they are perpendicular?

Back

Two lines are perpendicular if the product of their slopes is -1.

Front

If line C has a slope of -4, what is the slope of a line parallel to it?

Back

The slope of a line parallel to line C is -4.

Front

If line D has a slope of 1/2, what is the slope of a line perpendicular to it?

Back

The slope of a line perpendicular to line D is -2.