The bottom sign is division. The lefthandmost column of numbers, in the bottom left of the grid, is 9, over 1, over 8. 9 divided by 1 is 9. This new 9 divided by 8 is 1.125. When the sudoku is completed, shade in squares indicated by the co-ordinates underneath the grid. This will look like another mathematical symbol - its 9 letter name is the answer to this puzzle.

NOTE - I accidentally put the co-ordinates the wrong way around in each bracket, so (I,II) should be (II,I), (III,IV) should be (IV,III), etc.