When you receive your bank statements, all of the transactions that have been processed are listed. This includes deposits, debits and checks.
All transactions are usually listed in order of the date of transaction. Additionally, the checks are usually listed at the bottom of the statement.
If there is a gap between check numbers that you have written, it means that the missing checks have not been processed. This means that they have not been cashed or deposited.
Cos(x) = 1 at 0 and 2pi 360 and -360 is the same angle as 2pi so all of the above if you start at 0 and make a complete circle (360) you will be back at point 0.