There are several questions:

1) When a is proposed from the root sign, it should be |a|.

2) Other than that, there is nothing wrong with the sixth line.

3) Line 6 to Line 7, the boundary is wrong, it should be π, not 2π.

4) From line 7 to line 8, the constant is wrong and should be 32.

5) The integration of lines 8 to 9 is complicated and may need to be written.

The following is the operation of the eighth line: