## using Isolate in RootFinding...

In using Isolate in RootFinding to compute roots of a real polynomial, the output contains, say, z= some number.  How to get rid of the "z =" so that I can declare that "some number" to be some variable?

## How to 3d plot 3 variables ...

I have the following inequalty

, assuming all of the variables are positive.

How could I make a 3d plot with three axes for Г, K and N for example?

## "How can I solve this error in Maple?"...

5*x-7 = 3*x+2;
"(->)"
lhs(5*x-7 = 3*x+2) - rhs(5*x-7 = 3*x+2) = 0;
2 x - 9 = 0
[x]
isolate( 2*x-9 = 0, %ARG1 );
Error, (in isolate) 2*x-9 = 0 does not contain %ARG1
plz explain me what is this error?

## Error, (in MTM:-solve)...

Hello,

I want to determine the unknown out of the equation, and I do not know why I have such an error.

Error, (in MTM:-solve) {5*x-3 = 19} is not valid equation or expression

Why function Solve doesn't work?

## With(rootfinding) Isolate help!!...

I am having 26th degree polynomial univariate equation , I used Isolate to get the roots. but I am getting some extra roots which are not true they I even tried to substitute those roots in original equation then I got non zero answer instead of getting nearly zero answer.How is it possible??

equation looks like:

-12116320194738194778134937600000000*t^26+167589596741213731838990745600000000*t^24+1058345691529498270472972795904000000*t^22-4276605572538658673086219419648000000*t^20-23240154739806540070988490473472000000*t^18-5442849111209103187871341215744000000*t^16+49009931453396028716875310432256000000*t^14+74247033158233643322704589225984000000*t^12-2762178990802317464801412907008000000*t^10-25947900993773120244883450232832000000*t^8-7468990043547273070742668836864000000*t^6-567730116675454293925108383744000000*t^4+3703566799705707258760396800000000*t^2-4742330812072533924249600000000

Solutions i got:

[t = -4.162501845, t = -2.295186769, t = -1.300314688, t = -.8048430445, t = -0.6596008501e-1, t = -0.4212510777e-1, t = 0.4212510777e-1, t = 0.6596008501e-1, t = .8048430445, t = 1.300314688, t = 2.295186769, t = 4.162501845]

t=4.162501845 give me non zero answer when I substitute it in the equation given above:

## Fundamental theorem of calculus...

Hello people in mapleprime,

Though I wrote the title as Fundamental theorem of calculus,

what I am considering is just how to continue the chain of codes in calculation.

restart;

#I defined F__0 as

F__0:=x->Int(f(t),t=a..x);

#Then, the difference between a primitive function of f(x), F(x), and F__0 is no more than a constant C, so I write.

bb:=F(x)-F__0(x)=C;

#Then, substituting "a" into equation "bb", I obtain the value of F(a)

bb1:=subs(x=a,bb):cc:=simplify(%);

#Then, I substituted the value of C in "bb1" into "bb,"  obtaining the following "cc1."

cc1:=subs(isolate(cc,C),bb);

#And, then, I isolated the term of Int(f(t),t=a..x)  in cc1,

dd:=isolate(cc1,Int(f(t), t = a .. x));

#And, then, I substitute x=b into the outcome of dd, and obtain the final equation.

subs(x=b,dd);

Surely, with the above code, I could get the fundamental theorem. But, it looks in a little roundabout way.

So, I thought I would ask here about whether there aren't any better ways to do the fundamentally the same thing or

hints to improve the above code.

taro

## RootFinding[Isolate] vs solve...

For solving polynomial systems I used RootFinding[Isolate]. But after discussing the question http://www.mapleprimes.com/questions/211774-Roots-Of--Expz--1
I decided to compare Isolate and evalf(solve ([...], [...])). It seemed to me that solve some convenient. The only if in the equation there are integers as a real, they should be recorded with a decimal point. (For real solutions of this procedure should be used with (RealDomain).)  Examples:

SOLVE_ISOLATE.mw

I wonder why then the need Root Finding [Isolate]?

## Undesired expansion in solving...

In working on an answer to a recent question on MaplePrimes:
http://mapleprimes.com/questions/210948-Can-We-Trust-Maple

I noticed that in solving a "simple" system of two equations in two unknowns, potentially undesirable expansion occurs.
The two equations were only simple in the sense that the solving was very trivial, since the two unknowns occurred (almost) already isolated on the left:
eq1:=diff(x(t),t)=rhs1;
eq2:=1.2345*diff(v(t),t)=rhs2; #rhs2 is very complicated in the link given.
So in isolating I tried:
solve({eq1,eq2},{diff(x(t),t),diff(v(t),t)});
The resulting ode system took considerably longer to solve numerically than an unexpanded version.
It is trivial (of course) to do the solving without solve in this case.

Here is an extremely simple example, where the unknowns are already isolated, so that the equations themselves are actually the solution.

restart;
eq1:=a=b*(c+d);
solve(eq1,a); #No expansion
eq2:=e=b*(c+d)+f*(8+k);
solve({eq1,eq2},{a,e}); #Expanded:
{a = b*c+b*d, e = b*c+b*d+f*k+8*f}

Can expansion be avoided?

## Problem with "isolate expression for"...

Hello

when i am trying to isolate for Rev in the following expression

the program doesnt respond.do you know why?

## Isolate an expression...

Hi there

I'm trying to isolate (y1-3)2+(x1-1)in the equation 25(y1-3)2+200+100(x1-1)2=0.

I have tried isolate and solve, but solve coplains about solving for expressions (but when inputting i:=(x1,y1)->(y1-3)2+(x1-1)2 it still doesn't work), and isolate can only isolate either (y1-3)2 or (x1-1). Not both.

How can I do this with as few lines as possible?

Thanks

- Alex

## Can't solve this equation...

Hello everybody,

I guess my problem is a very little one, but I don't have any idea how to solve the following equation:

The equation is defined as follows:

gl1 := a = (arctan(b^2/(z*sqrt(b^2+b^2+z^2)))+b^2*z*(1/(z^2+b^2)+1/(z^2+b^2))/sqrt(b^2+b^2+z^2))/(2*pi);

z := solve(gl1, z);

Warning, solutions may have been lost

Does anybody of you have an idea how to solve this problem?

## Error, (in isolate) cannot isolate for a function ...

Hello,

Im solving 4 ODE equations with BC. im trying to shoot the initial value but im having this error:

""Error, (in isolate) cannot isolate for a function when it appears with different arguments""

anyone could help me???

 >
 >
 >
 >
 >
 >
 >
 >
 (1)
 >
 (2)
 >
 (3)
 >
 >
 Error, (in isolate) cannot isolate for a function when it appears with different arguments
 >

## Isolating Expressions...

Hi there,

I'm doing my first steps with Maple and am a little confused with a problem:
I want to solve something like

and expect the result to be z=-m*a. However I get empty brackets as result.
I tried to dig a little and I find that maple has problems isolating x1+x2+x3+x4

Error, (in isolate) x1*a+x2*a+x3*a+x4*a does not contain x1+x2+x3+x4

When I isolate it myself Maple even tells me they wouldn't be the same

false

I even reduced the problem to x1*a+x2*a and Maple still has problems with that. As this is a really simple problem I strongly assume the issue lies with the user. Can anyone help me there?

Thanks

## Fsolve and Isolate Missing Solutions...

To motivate some ideas in my research, I've been looking at the expected number of real roots of random polynomials (and their derivatives).  In doing so I have noticed an issue/bug with fsolve and RootFinding[Isolate].  One of the polynomials I came upon was

f(x) = -32829/50000-(9277/50000)*x-(37251/20000)*x^2-(6101/6250)*x^3-(47777/20000)*x^4+(291213/50000)*x^5.

We know that f(x) has at least 1 real root and, in fact, graphing shows that f(x) has exactly 1 real root (~1.018).  However, fsolve(f) and Isolate(f) both return no real roots.  On the other hand, Isolate(f,method=RC) correctly returns the root near 1.018.  I know that fsolve's details page says "It may not return all roots for exceptionally ill-conditioned polynomials", though this system does not seem especially ill-conditioned.  Moreover, Isolate's help page says confidently "All significant digits returned by the program are correct, and unlike purely numerical methods no roots are ever lost, although repeated roots are discarded" which is clearly not the case here.  It also seems interesting that the RealSolving package used by Isolate(f,method=RS) (default method) misses the root while the RegularChains package used by Isolate(f,method=RC) correctly finds the root.

All-in-all, I am not sure what to make of this.  Is this an issue which has been fixed in more recent incarnations of fsolve or Isolate?  Is this a persistent problem?  Is there a theoretical reason why the root is being missed, particularly for Isolate?

Any help or insight would be greatly appreciated.

## Solution of quite complicated equation in terms of...

This is my code for finding mode shapes and critical load for a bimaterial strut under buckling.

Although everything else is working fine but I have a problem while solving for critical load.

h_new := convert(series(h, P, 3), polynom):

h_new := convert(series(h, P, 3), polynom):

without converting to polynomial, the code is unable to solve for P. Even on conversion, for differnet S values, I need to change the truncation order of conversion (like for S=0.5, it would work with 3 but for other S values I have to change truncation (convert(series(h, P, 6), polynom)), which also causes the number of solutions of equation to change which causes problem with plotting of graphs of critical load that I need (basically I need lowest two plots), thereby restricts me from automating the code with a for loop. I need to test it for various S values and then later in code I need to put teh critical load back and check mode shapes for different a values.

Is there a better way to solve two variable equation to get one variable in terms of another(the equation is quite complicated, contains trigonometric expressions).

and also if I try to automate the analysis for different S and a values, teh process needs to put teh value back in P which changes everything and teh next time loop operates it just ruins everything. Also there are varied number of solutions of P_crit for differnet S values which makes it difficult to store those solutions during automation?

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