Horizontal Line Test
This applet can be used to determine whether a function is
onetoone
or not, and also to restrict the domain to some interval where the
function is onetoone.
 Enter a function of x in the input box.
 Drag the vertical slider up or down (or press the Play
button) to find the intersecting points of the graph and the horizontal
line.
 To see the xcoordinates of the intersection points, check
the “show coordinates”.
If we want to define an inverse function then we have to find
an interval where f(x) is onetoone.
 Drag the left and/or the right side of the blue segment
under the graph to restrict the domain.
Use the second button on the toolbar to drag the viewing
window, zoom in or zoom out if necessary.
Irina Boyadzhiev, 18 September
2013, Created with GeoGebra
