   |  R^1 = R      |  R^1 -&gt; R     |
&gt; &gt; |  2            |  R^2 = RxR    |  R^2 -&gt; R     |
&gt; &gt; |  3            |  R^3 = RxRxR  |  R^3 -&gt; R     |
&gt; &gt; |  ...          |  ...          |  ...          |
&gt; &gt; |  n            |  R^n          |  R^n -&gt; R     |
&gt; &gt; ¤~~~~~~~~~~~~~~~¤~~~~~~~~~~~~~~~¤~~~~~~~~~~~~~~~¤
&gt; &gt;
&gt; &gt; Now, it is typical to begin with the one-dimensional case
&gt; &gt; and gradually to work toward the multi-dimensional setting.
&gt; &gt; I