How do you find the slope of a line perpendicular to a slope 0?

3 Answers
May 9, 2018

It will of the type #x=k#.

Explanation:

This appears to be a bit complicated as normally we say that if slope of a line is #m#, slope of line perpendicular to it is #-1/m#, which means just take the reciprocal and change the sign.

For example if slope of a line is #3/7#, line perpendicular to it will have a slope of #-7/3#. And if slope of a line is #-2#, slope of line perpendicular to it will be #1/2#.

What do we do if we have to find the slope of a line perpendicular to a line of slope #0#? The problem is #1/0# is not defined.

Way out is even simpler. As equation of a line whose slope is #0# is of the type #y=k_1# (here #k_1# a constant is #y#-intercept - aline parallel to #x#-axis),

equation of line perpendicular to it will be #x=k#, where #k# is another constant. Note #k# is #x#-intercept of the line #x=k# and this line is vertical i.e. parallel to #y#-axis.

May 9, 2018

The slope of a line perpendicular to a line with a slope of #0# is undefined. The perpendicular line is a vertical line.

Explanation:

The slope of a line perpendicular to a line with a slope of #0# is undefined. The perpendicular line is a vertical line.

A line with a slope of #0# is a horizontal line. A vertical line would be perpendicular to the horizontal line, but the slope of a vertical line is undefined.

For example:

The following points will result in a vertical line because the x-coordinates are the same.

#(2,3)# and #(2,4)#

#m=(4-3)/(2-2)#

#m=1/0#, which is undefined.

The points represent a vertical line with an undefined slope.

https://www.wolframalpha.com/input/?i=Find+the+slope:+(2,3),(2,4)

May 9, 2018

You cannot find the slope.
You can only say that it will be a vertical line and the slope is undefined.

Explanation:

A line with a slope of #0# is a horizontal line.

A line which is perpendicular to a horizontal line is a vertical line.

However, the slope of a vertical line is undefined.

So you cannot find the slope. You can only say that it will be a vertical line and the slope is undefined.

This is because for any change in #y# values, there is no change in the #x# values.

Slope = #(Delta y)/(Delta x) = y/0#