Update 11_nearly_free_electron_model_solutions.md - typo

src/11_nearly_free_electron_model_solutions.md

@@ -155,7 +155,7 @@ $$
 $$
 where $\langle n-1|n\rangle$ is the overlap between two neighbouring wavefunctions:
 $$
-\langle n-1|n\rangle$ = 2\kappa\int_0^\infty e^{-\kappa|x-a/2|}e^{-\kappa|x+a/2|} = e^{-\kappa a}(1+\kappa a)
+\langle n-1|n\rangle = 2\kappa\int_0^\infty e^{-\kappa|x-a/2|}e^{-\kappa|x+a/2|} = e^{-\kappa a}(1+\kappa a)
 $$
 and
 $$