Please help!

Question

Answer the following for a body centered unit cell.

Crystalline Solids Program
Answers should be numerical,
set r = 4.0.

edge in terms of r, the lattice pt radius:
face diagonal in terms of r, the lattice pt radius:
body diagonal in terms of r, the lattice pt radius:

Answer 1

8
11.31

Answer 2

for a body centered cell,
edge(a): a=sqrt(8) x r
face(b): b=sqrt((a^2) + (a^2))
body(c): c=sqrt((a^2) + (b^2))

r=4, so plug it in (:

Answer 3

I plug in your equations and get 11.31, 16, and 19.6, and i still get the answers wrong

Answer 4

never mind, calculation error. Thanks!!