# Additional label on axis - 2D plot

I am finding a local maximum of a curve and I want to make the plot easier to read. I added a point to where the maximum is but I would also like to:

1) add a tick with text below it where the x value of the maximum is (saying "Xmax" or " X* ")

2) a dotted line from the point down to the x-axis.

Here is a simpler version of the plot I'm making:

maxi = FindMaximum[Cos[x], {x, 4, 8}];
coordin = {x /. maxi[[2]], First[maxi]};
Plot[Cos[x], {x, 0, 4 \[Pi]}, Epilog -> {PointSize[Large], Point[coordin]}]


I have pictures to better explain this but I'm not allowed to post images.

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"I have pictures to better explain this but I'm not allowed to post images." - maybe post a link to your images, and I (or somebody else) will put them in for you. –  Ｊ. Ｍ. Apr 23 '13 at 15:04

Is this what you want?

maxi = FindMaximum[Cos[x], {x, 4, 8}];
coordin = {x /. maxi[[2]], First[maxi]};
Plot[Cos[x], {x, 0, 4 \[Pi]},
Epilog -> {PointSize[Large], Point[coordin], Dashed,
Line[{coordin, {coordin[[1]], 0}}], Text["X", coordin + {0.5, 0}]}]


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:) close! how do you put the "X" below the x axis? –  LiaChica Apr 23 '13 at 15:26
How about change Text["X", coordin + {0.5, 0}] to Text["X", {coordin[[1]], -0.1}]? –  user0501 Apr 23 '13 at 15:29
Got it! Thank you! :-) –  LiaChica Apr 24 '13 at 10:31