Let's say x is longest side, y is shortest side and z is the other side. So we have some equations such that
(by the first sentence)
(by the second sentence)
(by the third sentence)
By the second equation, we have
and if we use it in the first equation, then 
. So 
Since, if we use it in the third equation the we have 
then 
Therefore
By the second equation, we have
Since
Therefore