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Horizontal lines have a slope of zero and are parallel to the x-axis. In terms of functions, if the slope field consists only of horizontal lines, it means that every tangent line has zero slope for all values of x.
The measure of steepness or incline between two points on a graph.
Vertical Lines: Lines with undefined slopes that run parallel to the y-axis.
Steepest Descent/Ascent Line: The tangent line with maximum positive/negative slope at any given point in the slope field.