Struct solution with x

Hello everyone,

I am working with an equation on which the following conditions apply:

assume(b>0)
assume(a>0)
assume(a, 'real')
assume(b, 'real')

When solving the equation with returnconditions = true, i am getting the following result:

ans = 
  struct with fields:
    a: [1×1 sym]
    parameters: [1×1 sym]
    conditions: [1×1 sym] 

Which in turn becomes:

struct.a = x
struct.parameters = x 
struct.conditions = 
in(x, 'real') & x ~= - (144535293678694037036996263388468*b)/550769126706406357900905808352195 - (32414720195132252810133684333137447606333932928886786234467989994^(1/2)*b*1i)/1101538253412812715801811616704390 & x ~= (32414720195132252810133684333137447606333932928886786234467989994^(1/2)*b*1i)/1101538253412812715801811616704390 - (144535293678694037036996263388468*b)/550769126706406357900905808352195 & x ~= 0 & (10680255103650670499995359170034131163219897411919919799173673439*b^3*x^5)/79837633165635972006615589284779352945345712957526101491630344520 - (55070065378198770734782937112491826444689537731357326839658245779*b^7*x)/1596752663312719440132311785695587058906914259150522029832606890400 - (52682521843631337410187030198853895179031908261767012193429299817*b^6*x^2)/239512899496907916019846767854338058836037138872578304474891033560 - (722821513198866414051031018767030783537554023560957917135176630303*b^5*x^3)/958051597987631664079387071417352235344148555490313217899564134240 - (94638163488239999525893552205606732378719408740871677041354524807*b^4*x^4)/95805159798763166407938707141735223534414855549031321789956413424 - (37596530622524706251454733767005997636263743780709487221228539*b^8)/16461367663017726186931049337067907823782621228355897214769143200 + (133756038408178157507705834783100115363513651202789647077864673153*b^2*x^6)/239512899496907916019846767854338058836037138872578304474891033560 + (90789175570872107684921442791045770758473169184763116518350393177*b*x^7)/79837633165635972006615589284779352945345712957526101491630344520 + x^8 == 0

I have no idea how to interpret this solution, can anyone help me with this?

Thank you in advance

[Vladimir Sovkov]

Notice, that every next assume cancells previous assumptions. Use assumeAlso instead.

Besides, assumtions of ...>0 already implies that the value is real, no need to specify it once more.

[Rik]

@Vladimir Sovkov

Your second remark is not true:

a=(1+1j);%create a complex variable
clc
a>0 %returns true

The documentation explains the < only looks at the real part of complex numbers.

[Vladimir Sovkov]

My second remark is true.

Try without assumptions

clear all
syms x
double(solve(x^2+1i==0,x))

ans =

-0.707106781186548 + 0.707106781186548i

0.707106781186548 - 0.707106781186548i

and with the assumtion

clear all
syms x
assume(x>0)
double(solve(x^2+1i==0,x))

ans =

0×1 empty double column vector

[Rik]

Strange. This must be an exception in the sym toolbox, which I don't have access to at this moment, so I can't run your code myself.

[Roy Cornelissen]

I think i might have found it. Is it possible that matlab returns x=a? Hence, the only

thing matlab did was substitute the value for which the equation should be solved (a)

with x.