Coefficient of linear expansion question

Dec 2013
4
0
Measurements of XRay scattering from an unidentified metal are made. The bragg peaks are θ = 50° and 46° for temperatures of 299K and 1250K respectively.

Calculate the linear expansion coefficient of the metal. This is given by
(1/L)(dL/dT)

The rate of change isn't uniform, so the differential form of the Bragg equation must be used. This is
δd / d=δθ / tan θ.

I don't know how to start this question, could somebody please help?

Thanks in advance. :)