∴BC= 13,
Tambu =CMBM=32,
So the answer is: BC= 13, tanB = 32;;
(2) As shown in the figure,
∫△DEF∽△ABC, while DE: AB = 2: 1.
The ratio of the perimeter of ∴△DEF to △ABC is 2: 1.
So the answer is: 2: 1