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<A NAME=GCD_switch>

<TITLE>GCD_switch</TITLE></A>
<b><a href=r37_idx.html>INDEX</a></b><p><p>



<B>GCD</B> _ _ _  _ _ _  _ _ _  _ _ _ <B>switch</B><P>
<P>
 
 <P>
<P>
When <em>gcd</em> is on, common factors in numerators and denominators of 
expressions are canceled. Default is <em>off</em>. 
<P>
<P>
 <P> <H3> 
examples: </H3>
<P><PRE><TT>

(2*(f*h)**2 - f**2*g*h - (f*g)**2 - f*h**3 + f*h*g**2
   - h**4 + g*h**3)/(f**2*h - f**2*g - f*h**2 + 2*f*g*h
   - f*g**2 - g*h**2 + g**2*h);
 

   2  2    2          2  2      2        3      3    4
  F *G  + F *G*H - 2*F *H  - F*G *H + F*H  - G*H  + H
  ---------------------------------------------------- 
    2      2        2                2    2        2
   F *G - F *H + F*G  - 2*F*G*H + F*H  - G *H + G*H


on gcd; 

ws; 

                 2
  F*G + 2*F*H + H
  ---------------- 
       F + G


e2 := a*c + a*d + b*c + b*d; 

  E2 := A*C + A*D + B*C + B*D 


off exp; 

e2; 

  (A + B)*(C + D)

</TT></PRE><P>Even with <em>gcd</em> off, a check is automatically made for comm
on variable 
and numerical products in the numerators and denominators of expression, 
and the appropriate cancellations made. Thus the example demonstrating the 
use of <em>gcd</em> is somewhat complicated. Note when 
<A HREF=r37_0256.html>exp</A> is off, 
<em>gcd</em> has the side effect of factoring the expression. 
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<P>
<P>