t t <lan1967 at mail.ru> writes:
> Hello, people!
> Sorry for disturbance.
> I got a question.
> I need to use one of the found roots for calculation.
> But when I use one of them g[2] to compare the program doesn't really
> do any comparison.
> How to use the root for comparison?
> Thank you for your attention.
>
> w:realroots(g^2-1);
> w[1];
> if (w[2]<2) then j:0;
> j;?
>
> [g=-1,g=1]
> g=-1
> (%o330) if g=-1<2 then j:0
> (%o331) j?
Hi,
There are two things that seem to be confusing you. Firstly, the second
element of w is the equation g=1:
(%i14) w:realroots(g^2-1);
(%o14) [g = - 1, g = 1]
(%i15) w[2];
(%o15) g = 1
To get the "1" bit, use the rhs() function:
(%i16) rhs(w[2]);
(%o16) 1
Now you want to check how big it is. Just testing "rhs(w[2]) < 2;"
doesn't work:
(%i18) rhs(w[2]) < 2;
(%o18) 1 < 2
because Maxima doesn't perform (in)equality tests like this unless you
tell it to. However, the is() function does what you need:
(%i19) is(rhs(w[2]) < 2);
(%o19) true
So I think you want something like:
(%i21) if (is(rhs(w[2]) < 2)) then j:0$
(%i22) j;
(%o22) 0
Rupert
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