What is the crystal structure for a crystal where the ratio of the squares of the angle peaks is 0.825?

I followed [this](https://www.physics.rutgers.edu/grad/506/materials%20crystal%20structure.pdf) and it gives an example of how to identify a crystal structure using XRD data. 


I have an unknown alkali halide where two peaks were found at $2\theta =25.66$ and $2\theta = 28.3$. I used a copper source for the x-rays. I need to figure out the crystal structure from this. Using the example in the link above, I got


$$\sin ^2 (\theta \_1)=0.04931022$$


$$\sin ^2 (\theta \_2)=0.05976132$$


Therefore,


$$\frac{\sin ^2 (\theta \_1)}{\sin ^2 (\theta \_2)} = 0.82511934$$


The PDF only mentions what the result will be for BCC (0.5) and FCC (0.75). Can I reliably conclude that this must be a FCC crystal? 


