# What is the slope perpendicular to the line y=10?

Feb 15, 2017

See the entire solution explanation below:

#### Explanation:

Because there is no $x$ term in this equation this is, by definition, a horizontal line where for any and all values of $x$, $y$ is $10$. And, by definition a horizontal line has slope $0$.

A line perpendicular to a horizontal line is a vertical line. A vertical line, by definition has a slope which is undefined.

Therefore the slope of any line perpendicular to $y = 10$ is undefined.