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in that it also shows how big oh behaves with respect to multiplication.
<P>
<BLOCKQUOTE> <b>Theorem</b><A NAME="theoremiv"> </A>
If <IMG WIDTH=118 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59227" SRC="img265.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img265.gif" > and <IMG WIDTH=36 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59241" SRC="img269.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img269.gif" > is a function whose value is non-negative
for integers <IMG WIDTH=38 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline59063" SRC="img241.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img241.gif" >,
then
<P> <IMG WIDTH=366 HEIGHT=16 ALIGN=BOTTOM ALT="displaymath59219" SRC="img321.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img321.gif" ><P></BLOCKQUOTE>
<P>
extbfProof
By Definition <A HREF="page57.html#defnbigoh" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page57.html#defnbigoh"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>, there exist integers <IMG WIDTH=16 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59043" SRC="img238.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img238.gif" >
and constant <IMG WIDTH=13 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59433" SRC="img322.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img322.gif" > such that
<IMG WIDTH=107 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59435" SRC="img323.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img323.gif" > for <IMG WIDTH=46 HEIGHT=23 ALIGN=MIDDLE ALT="tex2html_wrap_inline59075" SRC="img242.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img242.gif" >.
Since <IMG WIDTH=36 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59241" SRC="img269.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img269.gif" > is never negative,
<P> <IMG WIDTH=393 HEIGHT=16 ALIGN=BOTTOM ALT="displaymath59220" SRC="img324.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img324.gif" ><P>
Thus, <IMG WIDTH=230 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59441" SRC="img325.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img325.gif" >.
<P>
Theorem <A HREF="page60.html#theoremiv" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page60.html#theoremiv"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A> applies when we multiply a function, <IMG WIDTH=35 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59231" SRC="img267.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img267.gif" >,
whose asymptotic behavior is known to be <IMG WIDTH=60 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59279" SRC="img285.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img285.gif" >,
by another function <IMG WIDTH=36 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59241" SRC="img269.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img269.gif" >.
The asymptotic behavior of the result is simply <IMG WIDTH=116 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59449" SRC="img326.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img326.gif" >.
<P>
One way to interpret Theorem <A HREF="page60.html#theoremiv" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page60.html#theoremiv"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>
is that it allows us to do the following mathematical manipulation:
<P> <IMG WIDTH=500 HEIGHT=39 ALIGN=BOTTOM ALT="eqnarray1467" SRC="img327.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img327.gif" ><P>
I.e., Fallacy <A HREF="page59.html#fallacyi" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page59.html#fallacyi"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A> notwithstanding,
we can multiply both sides of the ``equation'' by <IMG WIDTH=36 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59241" SRC="img269.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img269.gif" >
and the ``equality'' still holds.
Furthermore, when we multiply <IMG WIDTH=60 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59279" SRC="img285.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img285.gif" > by <IMG WIDTH=36 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59241" SRC="img269.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img269.gif" >,
we simply bring the <IMG WIDTH=36 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59241" SRC="img269.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img269.gif" > inside the <IMG WIDTH=28 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline58163" SRC="img1.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img1.gif" >.
<P>
The last theorem in this section
introduces the <em>transitive property</em> of big oh:
<P>
<BLOCKQUOTE> <b>Theorem (Transitive Property)</b><A NAME=1473> </A>
<A NAME="theoremv"> </A>
If <I>f</I>(<I>n</I>)=<I>O</I>(<I>g</I>(<I>n</I>)) and <I>g</I>(<I>n</I>)=<I>O</I>(<I>h</I>(<I>n</I>))
then <I>f</I>(<I>n</I>)=<I>O</I>(<I>h</I>(<I>n</I>)).
</BLOCKQUOTE>
<P>
extbfProof
By Definition <A HREF="page57.html#defnbigoh" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page57.html#defnbigoh"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>, there exist two integers, <IMG WIDTH=16 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59249" SRC="img272.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img272.gif" > and <IMG WIDTH=16 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59251" SRC="img273.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img273.gif" >
and two constants <IMG WIDTH=13 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59253" SRC="img274.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img274.gif" > and <IMG WIDTH=13 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59255" SRC="img275.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img275.gif" > such that
<IMG WIDTH=94 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59475" SRC="img328.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img328.gif" > for <IMG WIDTH=47 HEIGHT=23 ALIGN=MIDDLE ALT="tex2html_wrap_inline59259" SRC="img277.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img277.gif" > and
<IMG WIDTH=96 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59479" SRC="img329.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img329.gif" > for <IMG WIDTH=47 HEIGHT=23 ALIGN=MIDDLE ALT="tex2html_wrap_inline59263" SRC="img279.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img279.gif" >.
<P>
Let <IMG WIDTH=119 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59265" SRC="img280.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img280.gif" > and <IMG WIDTH=63 HEIGHT=15 ALIGN=MIDDLE ALT="tex2html_wrap_inline59407" SRC="img313.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img313.gif" >. Then
<P> <IMG WIDTH=500 HEIGHT=63 ALIGN=BOTTOM ALT="eqnarray1478" SRC="img330.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img330.gif" ><P>
Thus, <I>f</I>(<I>n</I>)=<I>O</I>(<I>h</I>(<I>n</I>)).
<P>
The transitive property of big oh
is useful in conjunction with Theorem <A HREF="page60.html#theoremii" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page60.html#theoremii"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>.
Consider <IMG WIDTH=81 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline59489" SRC="img331.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img331.gif" > which is clearly <IMG WIDTH=39 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline59491" SRC="img332.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img332.gif" >.
If we add to <IMG WIDTH=35 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59231" SRC="img267.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img267.gif" > the function <IMG WIDTH=81 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline59495" SRC="img333.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img333.gif" >,
then by Theorem <A HREF="page60.html#theoremii" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page60.html#theoremii"><IMG ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A>,
the sum <IMG WIDTH=91 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59269" SRC="img282.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img282.gif" > is <IMG WIDTH=60 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59351" SRC="img306.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img306.gif" >
because <IMG WIDTH=169 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59501" SRC="img334.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img334.gif" >.
I.e., <IMG WIDTH=174 HEIGHT=24 ALIGN=MIDDLE ALT="tex2html_wrap_inline59503" SRC="img335.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img335.gif" >.
The combination of the fact that <IMG WIDTH=98 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline59505" SRC="img336.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img336.gif" >
<em>and</em> the transitive property of big oh,
allows us to conclude that the sum is <IMG WIDTH=39 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline59491" SRC="img332.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img332.gif" >.
<P>
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