Horizontal Line

What is a Horizontal line?
Horizontal lines are generally used in coordinate geometry.  Horizontal line is a straight line that runs from left to right.  In the coordinate plane, the horizontal line is a line parallel to x axis.

Horizontal Line Definition
In coordinate geometry, the horizontal line definition states that a horizontal line is a straight line which is on the coordinate plane where all points of x-coordinate on the line have the same y-coordinate.

Example of a Horizontal Line
A graph plotted for a relation given as y = 6 is an example of horizontal line. The relation y = 6 means the value of y is constant for all values of x and it will not change. So in the graph, at the position where the y axis value is 6, a horizontal line is drawn from left to right.  This line of y=6 will be parallel to x axis.

Horizontal Line Equation
All the points in this line will have the same Y-axis value of the coordinate plane.  It is represented by the equation: Horizontal Line Equation y = b

This equation of a horizontal line states that all over the horizontal line i.e. for all the values of x, the y coordinate has the same value b. Here b is the y-intercept.

Slope of Horizontal Line
Slope of a line is the measure of the change in the y value for every change in the x axis value along the given line. For a horizontal line, y value doesn't change. So, the slope of a horizontal line is zero: Horizontal Line slope = 0

Example: If y = 7, what is the slope of the line parallel to it?
Solution: The answer is zero, as y = 7 means y is constant for all values of x and so it is a horizontal line.  We know that slope of a horizontal line is zero.  Therefore Answer = 0.

Applications of Horizontal line
• Horizontal line is used to find out if a given function is one-to-one.  Usually a graph is drawn to represent a given function.  If the horizontal line intersects the graph two or more times, then the result says that the function is one-to-one.
• Horizontal lines are very much useful in photography to indicate that the image to be taken photo is at rest or stable.
• To find out if a function has an inverse function, horizontal line test is done.