> the left matrix in a matrix multiplication flipping over and crashing down on top of the right matrix. (or is that backwards?) Both ways work. A row from th

> the left matrix in a matrix multiplication flipping over and crashing down on top of the right matrix. (or is that backwards?) Both ways work. A row from the left matrix rotated 90° clockwise to line up with the rows of the right matrix gives you the coefficients to use to combine those rows into a row of the result matrix. Conversely, a column from the right matrix rotated 90° anticlockwise to line up with the columns of the left matrix gives you the coefficients to use to combine those columns into a column of the result matrix. I didn't fully understand that until I read Strang's book.