The (i,j)-th element of the Jacobian matrix is defined as the derivative of i-th function with respect to the j-th indeterminate.
jacobian(f, indets) --
  where f (polynomials) and indets (indeterminates) are
  vectors of RingElem, all belonging to the same PolyRing.
  Throws if both f and indets are empty
  (cannot determine the ring for constructing the 0x0 matrix).
| a_11 B | a_12 B | ... | a_1c B | 
| a_21 B | a_22 B | ... | a_2c B | 
| ... | |||
| a_r1 B | a_r2 B | ... | a_rc B | 
TensorMat(A, B) --
  where A and B are matrices with the same BaseRing.
2011
jacobian)
TensorMat