 | where a, b >= 0 if n is even | |
 | where a >= 0 and b > 0 if n is even (b not zero if n odd) |
|
 | if n is even | |
 | if n is odd |
| | where a, b >= 0 if n is even | |
| | where a >= 0 and b > 0 if n is even (b not zero if n odd) |
|
| | if n is even | |
| | if n is odd |