## Strategy Menu:

# Cases Command

Use the Cases command if you want to do a proof
by cases. If you select a given of the form *P*_{1}*P*_{2}...*P*_{n} and
give the Cases command, then Proof Designer will break the proof into the
cases *P*_{1}, *P*_{2}, ...,
*P*_{n}. You can also break your proof into cases *P*
and *P*, for any statement *P*.
To do this, select the goal you want to prove by cases and give the Cases
command. Proof Designer will ask you to type in the statement *P*
that you want to use to determine the two cases.

If you are using a given of the form
*P*_{1}*P*_{2}...*P*_{n} to determine the cases,
then parentheses in the given can affect what cases you get. For example,
if you select a given of the form *P**Q**R* and give the
Cases command, then you will get the three cases *P*, *Q*, and
*R*. But if your given has the form *P*(*Q**R*), then you
will get only two cases: *P* and *Q**R*. Thus, you may want to add or remove parentheses in
your given before using the Cases command. Too add or remove parentheses,
use the Reexpress command.