具有符号数学的矩阵给出了符号答案，而不是数字答案
Matrix with symbolic math gives a symbolic answer, not a numeric one
考虑以下矩阵
Ja(t1, t2, t3, t4, t5, t6) =
[ (sin(t5)*(cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)) - sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/5 - sin(t1)/100 - (219*sin(t1)*sin(t2))/1000 - (19*cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/100 - (21*cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000 + (21*sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000, (219*cos(t1)*cos(t2))/1000 + (sin(t5)*(cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)) - sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/5 - (19*cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/100 - (21*cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000 + (21*sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000, (sin(t5)*(cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) + cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5 - (19*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/100 - (21*cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000 - (21*cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000, (sin(t5)*(cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) + cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5 - (21*cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000 - (21*cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000, -(cos(t5)*(cos(t3)*cos(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) - sin(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5, 0]
[ cos(t1)/100 + (219*cos(t1)*sin(t2))/1000 + (29*cos(t1)*sin(t3))/1000 - (21*cos(t4)*(cos(t1)*sin(t3) - cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/1000 - (21*sin(t4)*(cos(t1)*cos(t3) + sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/1000 + (sin(t5)*(cos(t4)*(cos(t1)*sin(t3) - cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))) + sin(t4)*(cos(t1)*cos(t3) + sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))))/5 + (19*cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/100, (219*cos(t2)*sin(t1))/1000 - (sin(t5)*(cos(t3)*cos(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) - sin(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5 + (19*cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/100 + (21*cos(t3)*cos(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000 - (21*sin(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000, (29*cos(t3)*sin(t1))/1000 - (21*cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 + (21*sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 - (19*sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/100 + (sin(t5)*(cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))) - sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))))/5, (21*sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 - (21*cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 + (sin(t5)*(cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))) - sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))))/5, (cos(t5)*(cos(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))) + sin(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))))/5, 0]
[ 0, 0, (21*cos(t3)*cos(t4))/1000 - (29*cos(t3))/1000 - (21*sin(t3)*sin(t4))/1000 - (sin(t5)*(cos(t3)*cos(t4) - sin(t3)*sin(t4)))/5, (21*cos(t3)*cos(t4))/1000 - (21*sin(t3)*sin(t4))/1000 - (sin(t5)*(cos(t3)*cos(t4) - sin(t3)*sin(t4)))/5, -(cos(t5)*(cos(t3)*sin(t4) + cos(t4)*sin(t3)))/5, 0]
问题是当我提出我的论点时，MATLAB 不以数字方式计算矩阵，而是以符号形式保留它。
这是结果：
Ja(q(1),q(2),q(3),q(4),q(5),q(6)) =
[ sin(63/100)/100 + (219*sin(528276371951843/1125899906842624)*sin(63/100))/1000 + (19*cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/100 + (sin(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/5 + (21*cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000 - (21*sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000, (219*cos(528276371951843/1125899906842624)*cos(63/100))/1000 + (19*cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/100 + (sin(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/5 + (21*cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000 - (21*sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000, - (19*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/100 - (sin(59/125)*(cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) + cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5 - (21*cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000 - (21*cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000, - (sin(59/125)*(cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) + cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5 - (21*cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000 - (21*cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000, -(cos(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5, 0]
[ cos(63/100)/100 + (219*sin(528276371951843/1125899906842624)*cos(63/100))/1000 + (29*cos(63/100)*sin(157/125))/1000 + (19*cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/100 - (21*cos(157/250)*(cos(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/1000 - (sin(59/125)*(cos(157/250)*(cos(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))) + sin(157/250)*(cos(63/100)*cos(157/125) + sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))))/5 - (21*sin(157/250)*(cos(63/100)*cos(157/125) + sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/1000, (19*cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/100 - (219*cos(528276371951843/1125899906842624)*sin(63/100))/1000 + (sin(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5 + (21*cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000 - (21*sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000, (19*sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/100 - (29*cos(157/125)*sin(63/100))/1000 + (21*cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 - (21*sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 + (sin(59/125)*(cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))) - sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))))/5, (21*cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 - (21*sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 + (sin(59/125)*(cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))) - sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))))/5, -(cos(59/125)*(cos(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))) + sin(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))))/5, 0]
[ 0, 0, (21*cos(157/125)*cos(157/250))/1000 - (29*cos(157/125))/1000 - (21*sin(157/125)*sin(157/250))/1000 + (sin(59/125)*(cos(157/125)*cos(157/250) - sin(157/125)*sin(157/250)))/5, (21*cos(157/125)*cos(157/250))/1000 - (21*sin(157/125)*sin(157/250))/1000 + (sin(59/125)*(cos(157/125)*cos(157/250) - sin(157/125)*sin(157/250)))/5, -(cos(59/125)*(cos(157/125)*sin(157/250) + cos(157/250)*sin(157/125)))/5, 0]
有什么方法可以获得实数吗？
简答：使用 eval 对符号表达式进行数值计算，或使用 one of these options, f.e. double or vpa.
将其转换为特定类型
请注意 eval 可能比使用 double 慢两倍，但有时也会稍快一些
说明
问题在于 MATLAB 不会对您的符号表达式进行数值计算，它只会在数学上简化您的表达式。
示例：
syms x
my_function(x) = cos(x)
% exact algebraic solution is known:
my_function(0) % returns 1
my_function(pi) % returns -1
my_function(pi/2) % returns 0
my_function(pi/6) % returns 3^(1/2)/2
% result can only be numerically approximated:
my_function(3.1415) % returns cos(6283/2000)
my_function(1) % returns cos(1)
因此，MATLAB 能够在结果确切已知的情况下简化 cos 表达式。一般情况下，cos的结果只能进行数值计算，因此MATLAB在其answer中显示cos。
如果您想要数值结果，可以使用以下选项之一：
eval：用数字计算你的矩阵double：转换为双精度single: 转换为单精度int8 ：转换为 8 位整数（替代方案 int16、int32、int64）vpa：转换为可变精度算法，即它允许您指定结果的所需精度（有效数字位数）
有关详细信息，请参阅 Conversion Between Symbolic and Numeric
使用 eval 是一个好的选择吗？
正如 Sardar Usama 所指出的，使用 eval（评估字符串）通常是不好的做法：
但是，这是一样的吗eval？
不，我不这么认为。 help sym/eval returns（对比help eval）：
eval Evaluate a symbolic expression.
eval(S) evaluates the character representation of the
symbolic expression S in the caller's workspace.
同样使用MATLAB调试器指出是不同的函数。但是，完整的解释中提到它计算表达式的 character 表示，这也可以在源代码中看到：
s = evalin('caller',vectorize(map2mat(char(x))));
因此，它在内部使用 evalin，类似于 eval，来评估字符串。这可能不是很有效。
那么，我们也应该避免sym/eval吗？
也许不是，double 在内部使用 eval 来评估字符串：
Xstr = mupadmex('symobj::double', S.s, 0);
X = eval(Xstr);
区别在于sym/eval使用eval（evalin）作为原始字符表示，即整个表达式，而double使用它来解析最终的字符结果，即数值评估值。
结论：对于您的示例，double 似乎是合适的方法，因为它比使用 eval 快两倍。但是，对于以下示例，eval 稍快一些 (~15%)：
my_function(x) = cos(x);
for i=2:100
my_function(x) = my_function(x) + cos(i*x);
end
考虑以下矩阵
Ja(t1, t2, t3, t4, t5, t6) =
[ (sin(t5)*(cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)) - sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/5 - sin(t1)/100 - (219*sin(t1)*sin(t2))/1000 - (19*cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/100 - (21*cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000 + (21*sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000, (219*cos(t1)*cos(t2))/1000 + (sin(t5)*(cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)) - sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/5 - (19*cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/100 - (21*cos(t3)*cos(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000 + (21*sin(t3)*sin(t4)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/1000, (sin(t5)*(cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) + cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5 - (19*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/100 - (21*cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000 - (21*cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000, (sin(t5)*(cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) + cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5 - (21*cos(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000 - (21*cos(t4)*sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000, -(cos(t5)*(cos(t3)*cos(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) - sin(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5, 0]
[ cos(t1)/100 + (219*cos(t1)*sin(t2))/1000 + (29*cos(t1)*sin(t3))/1000 - (21*cos(t4)*(cos(t1)*sin(t3) - cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/1000 - (21*sin(t4)*(cos(t1)*cos(t3) + sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/1000 + (sin(t5)*(cos(t4)*(cos(t1)*sin(t3) - cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))) + sin(t4)*(cos(t1)*cos(t3) + sin(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))))/5 + (19*cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/100, (219*cos(t2)*sin(t1))/1000 - (sin(t5)*(cos(t3)*cos(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)) - sin(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2))))/5 + (19*cos(t3)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/100 + (21*cos(t3)*cos(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000 - (21*sin(t3)*sin(t4)*(cos(t1)*cos(t2) - sin(t1)*sin(t2)))/1000, (29*cos(t3)*sin(t1))/1000 - (21*cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 + (21*sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 - (19*sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))/100 + (sin(t5)*(cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))) - sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))))/5, (21*sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 - (21*cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))))/1000 + (sin(t5)*(cos(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))) - sin(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))))/5, (cos(t5)*(cos(t4)*(sin(t1)*sin(t3) - cos(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1))) + sin(t4)*(cos(t3)*sin(t1) + sin(t3)*(cos(t1)*sin(t2) + cos(t2)*sin(t1)))))/5, 0]
[ 0, 0, (21*cos(t3)*cos(t4))/1000 - (29*cos(t3))/1000 - (21*sin(t3)*sin(t4))/1000 - (sin(t5)*(cos(t3)*cos(t4) - sin(t3)*sin(t4)))/5, (21*cos(t3)*cos(t4))/1000 - (21*sin(t3)*sin(t4))/1000 - (sin(t5)*(cos(t3)*cos(t4) - sin(t3)*sin(t4)))/5, -(cos(t5)*(cos(t3)*sin(t4) + cos(t4)*sin(t3)))/5, 0]
问题是当我提出我的论点时，MATLAB 不以数字方式计算矩阵，而是以符号形式保留它。
这是结果：
Ja(q(1),q(2),q(3),q(4),q(5),q(6)) =
[ sin(63/100)/100 + (219*sin(528276371951843/1125899906842624)*sin(63/100))/1000 + (19*cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/100 + (sin(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/5 + (21*cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000 - (21*sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000, (219*cos(528276371951843/1125899906842624)*cos(63/100))/1000 + (19*cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/100 + (sin(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/5 + (21*cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000 - (21*sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/1000, - (19*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/100 - (sin(59/125)*(cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) + cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5 - (21*cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000 - (21*cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000, - (sin(59/125)*(cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) + cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5 - (21*cos(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000 - (21*cos(157/250)*sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000, -(cos(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5, 0]
[ cos(63/100)/100 + (219*sin(528276371951843/1125899906842624)*cos(63/100))/1000 + (29*cos(63/100)*sin(157/125))/1000 + (19*cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/100 - (21*cos(157/250)*(cos(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/1000 - (sin(59/125)*(cos(157/250)*(cos(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))) + sin(157/250)*(cos(63/100)*cos(157/125) + sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))))/5 - (21*sin(157/250)*(cos(63/100)*cos(157/125) + sin(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/1000, (19*cos(157/125)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/100 - (219*cos(528276371951843/1125899906842624)*sin(63/100))/1000 + (sin(59/125)*(cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)) - sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100))))/5 + (21*cos(157/125)*cos(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000 - (21*sin(157/125)*sin(157/250)*(cos(528276371951843/1125899906842624)*cos(63/100) + sin(528276371951843/1125899906842624)*sin(63/100)))/1000, (19*sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))/100 - (29*cos(157/125)*sin(63/100))/1000 + (21*cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 - (21*sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 + (sin(59/125)*(cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))) - sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))))/5, (21*cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 - (21*sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))))/1000 + (sin(59/125)*(cos(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))) - sin(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))))/5, -(cos(59/125)*(cos(157/250)*(sin(63/100)*sin(157/125) - cos(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100))) + sin(157/250)*(cos(157/125)*sin(63/100) + sin(157/125)*(cos(528276371951843/1125899906842624)*sin(63/100) - sin(528276371951843/1125899906842624)*cos(63/100)))))/5, 0]
[ 0, 0, (21*cos(157/125)*cos(157/250))/1000 - (29*cos(157/125))/1000 - (21*sin(157/125)*sin(157/250))/1000 + (sin(59/125)*(cos(157/125)*cos(157/250) - sin(157/125)*sin(157/250)))/5, (21*cos(157/125)*cos(157/250))/1000 - (21*sin(157/125)*sin(157/250))/1000 + (sin(59/125)*(cos(157/125)*cos(157/250) - sin(157/125)*sin(157/250)))/5, -(cos(59/125)*(cos(157/125)*sin(157/250) + cos(157/250)*sin(157/125)))/5, 0]
有什么方法可以获得实数吗？
简答：使用 eval 对符号表达式进行数值计算，或使用 one of these options, f.e. double or vpa.
请注意 eval 可能比使用 double 慢两倍，但有时也会稍快一些
说明
问题在于 MATLAB 不会对您的符号表达式进行数值计算，它只会在数学上简化您的表达式。
示例：
syms x
my_function(x) = cos(x)
% exact algebraic solution is known:
my_function(0) % returns 1
my_function(pi) % returns -1
my_function(pi/2) % returns 0
my_function(pi/6) % returns 3^(1/2)/2
% result can only be numerically approximated:
my_function(3.1415) % returns cos(6283/2000)
my_function(1) % returns cos(1)
因此，MATLAB 能够在结果确切已知的情况下简化 cos 表达式。一般情况下，cos的结果只能进行数值计算，因此MATLAB在其answer中显示cos。
如果您想要数值结果，可以使用以下选项之一：
eval：用数字计算你的矩阵double：转换为双精度single: 转换为单精度int8：转换为 8 位整数（替代方案int16、int32、int64）vpa：转换为可变精度算法，即它允许您指定结果的所需精度（有效数字位数）
有关详细信息，请参阅 Conversion Between Symbolic and Numeric
使用 eval 是一个好的选择吗？
正如 Sardar Usama 所指出的，使用 eval（评估字符串）通常是不好的做法：
但是，这是一样的吗eval？
不，我不这么认为。 help sym/eval returns（对比help eval）：
eval Evaluate a symbolic expression. eval(S) evaluates the character representation of the symbolic expression S in the caller's workspace.
同样使用MATLAB调试器指出是不同的函数。但是，完整的解释中提到它计算表达式的 character 表示，这也可以在源代码中看到：
s = evalin('caller',vectorize(map2mat(char(x))));
因此，它在内部使用 evalin，类似于 eval，来评估字符串。这可能不是很有效。
那么，我们也应该避免sym/eval吗？
也许不是，double 在内部使用 eval 来评估字符串：
Xstr = mupadmex('symobj::double', S.s, 0); X = eval(Xstr);
区别在于sym/eval使用eval（evalin）作为原始字符表示，即整个表达式，而double使用它来解析最终的字符结果，即数值评估值。
结论：对于您的示例，double 似乎是合适的方法，因为它比使用 eval 快两倍。但是，对于以下示例，eval 稍快一些 (~15%)：
my_function(x) = cos(x);
for i=2:100
my_function(x) = my_function(x) + cos(i*x);
end