Y-intercept

Last updated
Graph
y
=
f
(
x
)
{\displaystyle y=f(x)}
with the
x
{\displaystyle x}
-axis as the horizontal axis and the
y
{\displaystyle y}
-axis as the vertical axis. The
y
{\displaystyle y}
-intercept of
f
(
x
)
{\displaystyle f(x)}
is indicated by the red dot at
(
x
=
0
,
y
=
1
)
{\displaystyle (x=0,y=1)}
. Y-intercept.svg
Graph with the -axis as the horizontal axis and the -axis as the vertical axis. The -intercept of is indicated by the red dot at .

In analytic geometry, using the common convention that the horizontal axis represents a variable and the vertical axis represents a variable , a -intercept or vertical intercept is a point where the graph of a function or relation intersects the -axis of the coordinate system. [1] As such, these points satisfy .

Contents

Using equations

If the curve in question is given as the -coordinate of the -intercept is found by calculating . Functions which are undefined at have no -intercept.

If the function is linear and is expressed in slope-intercept form as , the constant term is the -coordinate of the -intercept. [2]

Multiple -intercepts

Some 2-dimensional mathematical relationships such as circles, ellipses, and hyperbolas can have more than one -intercept. Because functions associate -values to no more than one -value as part of their definition, they can have at most one -intercept.

-intercepts

Analogously, an -intercept is a point where the graph of a function or relation intersects with the -axis. As such, these points satisfy . The zeros, or roots, of such a function or relation are the -coordinates of these -intercepts. [3]

Functions of the form have at most one -intercept, but may contain multiple -intercepts. The -intercepts of functions, if any exist, are often more difficult to locate than the -intercept, as finding the -intercept involves simply evaluating the function at .

In higher dimensions

The notion may be extended for 3-dimensional space and higher dimensions, as well as for other coordinate axes, possibly with other names. For example, one may speak of the -intercept of the current–voltage characteristic of, say, a diode. (In electrical engineering, is the symbol used for electric current.)

See also

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References

  1. Weisstein, Eric W. "y-Intercept". MathWorld--A Wolfram Web Resource. Retrieved 2010-09-22.
  2. Stapel, Elizabeth. "x- and y-Intercepts." Purplemath. Available from http://www.purplemath.com/modules/intrcept.htm.
  3. Weisstein, Eric W. "Root". MathWorld--A Wolfram Web Resource. Retrieved 2010-09-22.