Bragg: n=1, λ=d ⇒ sin θ = 1/2, θ = π/6 (canonical first-order reflection)

Sympy-exact symbolic witness of Bragg's law evaluated at the canonical first-order reflection with λ = d — the textbook anchor for crystallography intuition. Setup: set n = 1 (first-order diffraction), λ = d (the wavelength equals the…