![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=981fdd3fada9d766d81e7545a5551e8c.png\")
plane is the graph of a function of ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=8da2268e35b6b6daab9c47f71c4c8bf4.png\")
if and only if no vertical line intersects the curve more than once.Vertical Line Test :
\ A curve in the plane is the graph of a function of if and only if no vertical line intersects the curve more than once.
Observe the graph.
\Draw a vertical line at ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=9ce6b39351f84a1aabdd95bc4e6a257a.png\")
, the line touches the curve more than once.
The graph of the function fails the vertical line test.
\Hence by the definition of vertical line test, the graph is not a function of ![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=8da2268e35b6b6daab9c47f71c4c8bf4.png\")
. \ \
\
No, the graph is not a function of .