Rule of Sarrus: To calculate the determinant of a 3x3 matrix, add the products along the solid diagonals and subtract the products along the dashed diagonals. I have an exam in linear algebra today, and this rule is very handy. But it is mentioned nowhere in my textbook, which I now resent greatly. If you ask me, the only thing the text has on Wikipedia are the exercises and the paper to write on. Then again it’s also heavy and not free.

Rule of Sarrus: To calculate the determinant of a 3x3 matrix, add the products along the solid diagonals and subtract the products along the dashed diagonals.

I have an exam in linear algebra today, and this rule is very handy. But it is mentioned nowhere in my textbook, which I now resent greatly. If you ask me, the only thing the text has on Wikipedia are the exercises and the paper to write on. Then again it’s also heavy and not free.