Xray reflection

jbowers9

1. The problem statement, all variables and given/known data

X-rays 1.54 angstrom reflected off copper powder
@ 21.65º
25.21º
37.06º
44.96º
47.58º

2. Relevant equations

nλ = 2d sin(Θ) ; the Bragg equation

3. The attempt at a solution

The cubic latice is face centered at d110? 5 planes?
I tried plotting sin(Θ) vs. n to get the slope and calculate a, but it doesn't seem right?
How do I find the length of an edge of the unit cell and what is the cubic lattice?