Question

求大神解决matlab问题！

[x,y,z]=solve('1245572133718800698226781/703687441776640000000 - (776609*y)/20000 - (40122129979280075*z)/1125899906842624 - (38626517211016134611*x)/562949953421312000=0','(x-22.6853)/cosd(51.3402)=(y-17.9944)/cosd(38.6598)=(z-13.6981)/cosd(52.0148))','x','y','z')
警告: Support of strings that are not valid variable names or define a number will be removed in a future release. To create symbolic expressions, first create symbolic variables and then use operations on them.
> In sym>convertExpression (line 1536)
In sym>convertChar (line 1441)
In sym>tomupad (line 1198)
In sym (line 177)
In solve>getEqns (line 405)
In solve (line 225)
警告: Support of strings that are not valid variable names or define a number will be removed in a future release. To create symbolic expressions, first create symbolic variables and then use operations on them.
> In sym>convertExpression (line 1536)
In sym>convertChar (line 1441)
In sym>tomupad (line 1198)
In sym (line 177)
In solve>getEqns (line 405)
In solve (line 225)
错误使用 symengine
Unexpected ')'.

出错 sym>convertExpression (line 1543)
s = mupadmex({x});

出错 sym>convertChar (line 1441)
s = convertExpression(x);

出错 sym>tomupad (line 1198)
S = convertChar(x);

出错 sym (line 177)
S.s = tomupad(x);

出错 solve>getEqns (line 405)
a = sym(a);

出错 solve (line 225)
[eqns,vars,options] = getEqns(varargin{:});

Answer 1

由于题主现在使用的matlab是高版本，而你提供的代码在低版本上使用是没有问题的。所以你应该这样来写：

sysm x y z

[x,y,z]=vpasolve(1245572133718800698226781/703687441776640000000 - (776609*y)/20000 - (40122129979280075*z)/1125899906842624 - (38626517211016134611*x)/562949953421312000==0,(x-22.6853)/cosd(51.3402)==(y-17.9944)/cosd(38.6598),(y-17.9944)/cosd(38.6598)==(z-13.6981)/cosd(52.0148))

运行结果

Answer 2

function turev_s(x, y, d, r) 
f = sym(x);
n = length(symvar(f)); 
if n == 1
    s = diff(f,y);    
    sade = simplify(s)
    pretty(s)
    if r ~= 0
        sonuc = double(subs(f,{d},{r}));
    end
elseif n == 2
    s = diff(f,y);
    sade = simplify(s)
    pretty(s) 
    if r ~= 0
        sonuc = double(subs(f,{d},{r}));
    end
elseif n == 3
    s = diff(f,y);
    sade = simplify(s)
    pretty(s) 
    if r ~= 0
        sonuc = double(subs(f,{d},{r}));
    end
end
fprintf('Sonuc = %.4f\n',sonuc);
end