MATLAB function cross can be applied to symbolic object but Documentation does not explain?

syms x y z
vec1=[x y z];
vec2=[x y z];
cross(vec1,vec2)

Answer 1

[Ameer Hamza]

It works fine in R2020b, are you using an older release?

syms x y z
vec1 = [x y z];
vec2 = [x y z];
x = cross(vec1, vec2);

Result

>> x
x =
[0, 0, 0]

[Chuguang Pan]

I am using R2015a, it works fine. The Documentation says that cross function's input argument can be numerical value, it does not say it can accept symbolic vectors.

[Ameer Hamza]

Yes, you are right. Even in R2020b, the symbolic toolbox does not have separate documentation for cross-function. I think it is not officially supported; however, if you look at the implementation of cross()

edit cross

you can see that it just uses simple arithmetic operations, which are also supported for symbolic variables. So, maybe it "unintentionally" got support for symbolic variables too.

[Walter Roberson]

Especially back in those days, a lot of the numeric functions did not check specifically that their arguments were numeric. They just went ahead with the calculations, and if the calculations happened to involve an operation not possible on the variable type you were using, you would get an error in that particular operation.

[Ameer Hamza]

Also, inside cross.m file, it specifically mentions that it supports single and double classes. However, it works fine for other datatypes too

>> a = randi(10, 1, 3);
b = randi(10, 1, 3);
>> cross(a, b)
ans =
   -14    37   -10
>> cross(int8(a), b)
ans =
  1×3 int8 row vector
   -14    37   -10