##### find an equation perpendicular to y=4

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Find an equation for the line through (2,2) that is perpendicular to y=4 then graph both lines. Since the slop is 0, is the line perpendicular to y=4 undefined?

Sep 14th, 2015

Hello!

Line y=4 is a horizontal line. Therefore any perpendicular line is vertical and have an equation x=b. For this line to go through the point (2, 2) b must be 2.

The slope of the line y=4 is really 0. So the slope of the perpendicular line is undefined, but the perpendicular line itself is defined.

If you really need a graph of these lines, tell me.

Sep 14th, 2015

Hello, thank you! This helps a lot. I could use a graph of this. When I go to graph the first point will it be 0,4? Then the next one would be 2,2?

Sep 14th, 2015

The graph is here: https://www.desmos.com/calculator/ntjy0msykp

The first point for the line x=2 is (2, 2) -- it is given. The second point is any other point with x=2 (for example, (2,0) or (2, 4)).

Sep 14th, 2015

Okay thank you. Did you simply figure this answer out by looking at the question or did you use the point slope equation to solve this? Just curious in case I have another question like this one.

Sep 14th, 2015

The former, I didn't use slope (because this case is so specific). If the slope of the first line would be not zero, use slope solution.

Sep 14th, 2015

Thank you! When you graphed the points did you use 2,2 for the other point?

Sep 14th, 2015

I used (2, 2) as the first point and (2, 0) as the second (for x=2).

Sep 14th, 2015

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Sep 14th, 2015
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Sep 14th, 2015
Dec 5th, 2016
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