Update 3_drude_model_solutions.md - fix in 4.3

src/3_drude_model_solutions.md

@@ -129,11 +129,11 @@ Refer to the lecture notes
 3.
 
 $$
-\sigma_{xx} \approx \frac{\rho_{yy}}{1 + \rho_{xy}^2}
+\sigma_{xx} = \frac{\rho_{xx}}{\rho_{xx}^2 + \rho_{xy}^2}
 $$
 
 $$
-\sigma_{xy} \approx \frac{-\rho_{xy}}{1 + \rho_{xy}^2}
+\sigma_{xy} = \frac{-\rho_{yx}}{\rho_{xx}^2 + \rho_{xy}^2}
 $$
 
-This describes [Lorentzian](https://en.wikipedia.org/wiki/Spectral_line_shape#Lorentzian).
+This describes a [Lorentzian](https://en.wikipedia.org/wiki/Spectral_line_shape#Lorentzian).