Can't get my multidimensional array to work

1

so i tried declaring a multidimensional array and testing it with the following code:

var tpoint:Array = new Array(new Array());
tpoint[1][2]=7;
trace(tpoint[1][2]);

but the output is undefined. if i replace both the 1’s and the 2’s with 0’s, then it outputs a 7… so what am i doing wrong here? in the tutorials about MD arrays that i’ve read, the author always declares his arrays as a list, but the variables in my array are going to be declared dynamically, so i don’t know how to go about it…