R - Compute Cross Product of Vectors (Physics)

Question

What am I doing wrong?

> crossprod(1:3,4:6)
     [,1]
[1,]   32

According to this website:http://onlinemschool.com/math/assistance/vecto

Answer 1

crossProduct <- function(ab,ac){
  abci = ab[2] * ac[3] - ac[2] * ab[3];
  abcj = ac[1] * ab[3] - ab[1] * ac[3];
  abck = ab[1] * ac[2] - ac[1] * ab[2];
  return (c(abci, abcj, abck))
}