deprecated.xml: Explain rising to the power of a negative number (GH-3913)

Co-authored-by: Christoph M. Becker <[email protected]>

Author: mmalferov

appendices/migration84/deprecated.xml

@@ -84,9 +84,13 @@ function foo(T1 $a, ?T2 $b, T3 $c) {}
    <simpara>
     Raising a number to the power of a negative number is equivalent to taking
     the reciprocal of the number raised to the positive opposite of the power.
+    That is, <literal>10<superscript>-2</superscript></literal> is the same as
+    <literal>1 / (10<superscript>2</superscript>)</literal>.
     Therefore raising <literal>0</literal> to the power of a negative number
-    corresponds to dividing by <literal>0</literal>.
-    Thus, this behaviour has been deprecated.
+    corresponds to dividing by <literal>0</literal>, i.e.
+    <literal>0<superscript>-2</superscript></literal> is the same as
+    <literal>1 / (0<superscript>2</superscript>)</literal>, or
+    <literal>1 / 0</literal>. Thus, this behavior has been deprecated.
    </simpara>
 
    <simpara>