assign numerical value from a previous line now solved...
Subject: assign numerical value from a previous line now solved...
From: William Porter
Date: Sat, 17 Jul 2010 10:03:50 -0700
Hello all,
Subject: assign numerical value from a previous line
Thank you Zbigniew and Robert Dodier. Zibgniew did solve the problem and
Robert discovered in the text that the issue was not solved according to the
question I gave. Actually it was solved by Zibigniew, the error was on my
part. -x/(2*d) is the derivative of x^2+d*y*4+d^2*(-4) and its values are 1
and -1. The [x=-10, x=10] is the values when y=0. And Robert gave an
alternative to assignments.
The expressions are now solved, regarding assignments.
(%i1) e1: x^2+d*y*4+d^2*(-4);
2 2
(%o1) 4 d y + x - 4 d
(%i2) e2: solve(e1, y);
2 2
x - 4 d
(%o2) [y = - ---------]
4 d
(%i3) e3: diff(e2,x,1);
x
(%o3) [0 = - ---]
2 d
(%i4) en:5;
(%o4) 5
(%i5) e4: subst([y=0,d=en], e1);
2
(%o5) x - 100
(%i6) e5: solve(e4, x);
(%o6) [x = - 10, x = 10]
(%i7) %phi[1] : e3;
x
(%o7) [0 = - ---]
2 d
(%i8) %phi[2] : e3;
x
(%o8) [0 = - ---]
2 d
(%i9) subst([e5[1], d=5],%phi[1]);
(%o9) [0 = 1]
(%i10) subst([e5[2], d=5],%phi[2]);
(%o10) [0 = - 1]
(%i11)
Regards,
Bill
William Porter
wporter at omegapar.com