Align 1st row of Grid different from the other rows

Question

The grid formed below aligns its columns as I want on the decimal point:

x = 2. Pi/24 Range[0, 5];
data = Transpose[{x, Chop@Sin[x]}];

Grid[data, Alignment -> {"."}]

Now I want to prepend a row to the grid with its two items centered. I tried the following, which if I understand the documentation, ought to do it:

Grid[Prepend[data, {"x", "sin x"}], Alignment -> {Center, {"."}}]

But that just centers all entries in each column.

How do I get just the first row's entries to be centered but the remaining rows to be aligned on the decimal point?

Answer 1

This should do it. In Alignment docs under Generalizations & Extensions.

Grid[Prepend[data, {"x", "sin x"}],
 Alignment -> {".", Automatic, {{1, 1} -> Center, {1, 2} -> Center}}]

There is an odd ItemSize issue in the first column though, stemming from the "." alignment algorithm as I recall. E.g.

x = 2. Pi/24 Range[0, 5];
data = Transpose[{x, Chop@Sin[x], Chop@Cos[x]}];

Grid[Prepend[data, {"x", "sin x", "cos x"}],
 Alignment -> {".", Automatic,
   {{1, 1} -> Center, {1, 2} -> Center, {1, 3} -> Center}},
 Frame -> All]

Answer 2

The following, using Item as suggested in https://mathematica.stackexchange.com/a/180225/148, does what I want, although I'd still prefer a simpler way using the spec recycling aspect of Alignment to avoid Item.

hdr = Item[Text[#], Alignment -> Center] & /@ {"x", "sin x"}; Grid[
 Prepend[data, hdr], Alignment -> "."]