# Making a plotted curve interactive

Is it possible to make a plotted curve interactive in the sense that when hovering over it a line is drawn from the "hovered" point to one (or both) of the axes. I did do my homework, I just can't figure it out.

Edit: Let's say I plot this curve:

Manipulate[Plot[Sin[a x],{x,0,Pi}],{a,1,5}]


Whenever the mouse hovers over a point on the curve a line is drawn from that point to the x-axis.

Something like this?

DynamicModule[{mp, x, y, fun},
fun[x_, a_] := Sin[a x];
Manipulate[
mp = MousePosition["Graphics"];
If[mp === None,
epi = {},
{x, y} = mp;
epi =
If[
Abs[y - fun[x, a]] < 0.1,
Line[{{x, 0}, {x, fun[x, a]}}],
{}
]
];
Plot[fun[x, a], {x, 0, Pi}, Epilog -> epi]
, {a, 1, 5}
]
]


 Manipulate[Plot[Sin[a x], {x, 0, 10},
Epilog -> {Red, Thick, Line[Dynamic[{{First[pt], 0},
{First[pt],Sin[a First[pt]]}}]]}],
{a, 1, 5},
{{pt, {0, 0}}, ControlType -> Locator, Appearance -> None, AutoAction -> True}]


 Manipulate[
Plot[Sin[a x], {x, 0, 10},
Epilog -> {Red, Thick, Line[Dynamic@{{First[pt], 0}, {First[pt], Sin[a First[pt]]}}],
Line[Dynamic@{{0, Sin[a First[pt]]}, {First[pt], Sin[a First[pt]]}}],
Black, PointSize[.03], Point[Dynamic@{First[pt], Sin[a First[pt]]}]}],
{a, 1, 5}, {{pt, {0, 0}}, ControlType -> Locator, Appearance -> None,
AutoAction -> True}]