Use the fact that any physical operator 
must be Hermitian
( 
for all functions
and 
) to show that the wave funcions 
and 
of any two pure states with respect to the
observable 
of different values 
must obey
. This property is known as
``orthogonality.''
Hint: Consider the relationships among
, 
, and 
and be sure to use the fact that is
Hermitian.