Assertion: line's slope | /r/HasProperty | undefined
Facets:
Source sentences:
text: If a line is vertical the slope is undefined (see below).
text: The formula fails for a vertical line, parallel to the y axis (see Division by zero), where the slope can be taken as infinite, so the slope of a vertical line is considered undefined.
text: The slope of a vertical line is undefined
text: The slope is undefined ... and where does it cross the Y-Axis?