'The slope of a line parallel to the horizontal axis is ZERO .
A planar Cartesian coordinate system is a coordinate system in which each point is uniquely identified by a pair of numeric coordinates. A numeric coordinate is a signed distance to a point on two fixed vertical lines measured in the same length unit.
Graphs a function by plotting points on the coordinate plane (sometimes called the Cartesian plane). A coordinate plane is a grid of horizontal and vertical number lines that intersect at a point called the origin.
The horizontal axis represents the direction of change and continuity. A series of measurements on an analog signal requires both time (horizontal axis) and amplitude (vertical axis) values.
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