Lines: Miscellaneous!

Vertical and Horizontal Lines

The vertical line x=5 is drawn in blue. Notice that the x coordinate of all the points on the blue line is 5.

The horizontal line y=3 is drawn in green. Notice that the y coordinate of all the points on the green line is 3.

Parallel Lines

Parallel lines have the same slope.

Move the slider ‘b’ to see a set of lines that all have the same slope.

Perpendicular Lines

Suppose we sit a box that measures 5 by 3 on the x axis as shown below. The diagonal line drawn has slope -5/3.

Rotate the box to see that when a line is rotated a full 90 degrees, the rise and run are interchanged, and a negative slope becomes a positive slope.

In general, if slope of line 1 is

    \[\frac{a}{b}\]

and if slope of line 2 is

    \[-\frac{b}{a}\]

then lines 1 and 2 are perpendicular to each other.


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