Inversion at the 13th and the 10th in fugue BWV 885

In measure 32 Bach uses the inversion at the 13th:

The following images compare measures 32 - 33 with measures 13 - 14:

This is the table of the inversion at the 13th. Sixths inverts as octaves, thirds as fourths and octaves as sixths:

1	2	3	4	5	6	7	8	9	10	11	12	13
13	12	11	10	9	8	7	6	5	4	3	2	1

In measures 36 to 39, Bach uses inversion at the 10th:

Once more, we will use the inversion table to confirm that Bach is using the inversion at the 10th. This is the table of the inversion at the 10th. Sixths inverts as fifths, thirds as octaves and octaves as thirds:

1	2	3	4	5	6	7	8	9	10
10	9	8	7	6	5	4	3	2	1