What is the slope of a line parallel to the y-axis?

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Answer 1 · 2014-10-06T05:16:01

Parallel lines have the same slope.

Vertical lines have an undefined slope.

The $y$ -axis is a vertical.

A line that is parallel to the $y$ -axis also has to be vertical.

The slope of a line parallel to the $y$ -axis has a slope that is undefined.

Answer 2 · 2017-02-21T04:42:06

A line parallel to the y-axis - a.k.a. vertical line has no slope!

Slope is defined as $rise$ divided by $run$

A line parallel to the $y$ axis is a vertical line that has no $run$ so it defies the definition.

A line parallel to the $x$ axis has no $rise$ but it follows the definition because a slope of $0$ can be calculated.