Hello, WeBWorK produces weird bug if we deal with vector functions (allowing ijk notation) and student submits answer with incorrect number of components.
See the attached file. The correct answer is <0,0,x> or x*k. If the student enters <0,0,0,0,x>, he/she gets "wrong" message. If he/she then enters a correct solution <0,0,x>, he/she gets strange error message. Sumitting 0 removes this strange message and submiting the correct answer works after this procedure. However, I think that there is something wrong in the ijk-notation parser.
Removing the line which accepts ijk notation from the pg files solves the problem. However, in vector calculus we often use this notation and it would be nice to keep the possibility give the answer in ijk notation.
Thank you for all suggestions.