∴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