[system] / trunk / webwork-modperl / htdocs / helpFiles / IntervalNotation.html Repository: Repository Listing bbplugincoursesdistsnplrochestersystemwww

View of /trunk/webwork-modperl/htdocs/helpFiles/IntervalNotation.html

Sun Aug 21 23:54:27 2005 UTC (7 years, 9 months ago) by jj
File size: 1949 byte(s)
```Update help file to match some recent changes in checking of answers which
are intervals.
```

```    1 <html>
3 <title>WeBWorK Help: Interval Notation</title>
7
8 <h4 align="center">
9 Using Interval Notation
10 </h4>
11
12 <ul>
13
14 <li> If an endpoint is included, then use <tt>[</tt> or <tt>]</tt>.
15 If not, then use <tt>(</tt> or <tt>)</tt>.  For example, the interval
16 from -3 to 7 that includes 7 but not -3 is expressed <tt>(-3,7]</tt>.
17
18 <br>
19 <br>
20
21 <li> For infinite intervals, use <tt>Inf</tt>
22 for <font size="+2">&#8734;</font> (infinity) and/or
23 <tt>-Inf</tt> for <font size="+2">-&#8734;</font> (-Infinity).  For
24 example, the infinite interval containing all points greater than or
25 equal to 6 is expressed <tt>[6,Inf)</tt>.
26
27 <br>
28 <br>
29
30 <li> If the set includes more than one interval, they are joined using the union
31 symbol U.  For example, the set consisting of all points in (-3,7] together with all points in [-8,-5) is expressed <code>[-8,-5)U(-3,7]</code>.
32
33 <br>
34 <br>
35
36 <li> If the answer is the empty set, you can specify that by using
37      braces with nothing inside: <code> { } </code>
38
39 <br>
40 <br>
41
42 <li> You can use <code>R</code> as a shorthand for all real numbers.
43   So, it is equivalent to entering <code>(-Inf, Inf)</code>.
44
45 <br>
46 <br>
47
48 <li> You can use set difference notation.  So, for all real numbers
49   except 3, you can use <code>R-{3}</code> or
50   <code>(-Inf, 3)U(3,Inf)</code> (they are the same).  Similarly,
51   <code>[1,10)-{3,4}</code> is the same as <code>[1,3)U(3,4)U(4,10)</code>.
52
53 <br>
54 <br>
55
56
57 <li> WeBWorK will <b>not</b> interpret <tt>[2,4]U[3,5]</tt> as equivalent
58  to <tt>[2,5]</tt>, unless a problem tells you otherwise.
59 All sets should be expressed in their simplest interval notation form, with no
60 overlapping intervals.
61
62 </ul>
63
64 <script language="JavaScript">
65 document.write(" <center> <p><input type=\"button\" value=\"Close this window\" name=\"close\" onClick=\"window.close()\"></p> </center> ");
66 </script>
67
68 </body></html>
```