Update 7_tight_binding.md - typo fix

e33ccfab · T. van der Sar · 5fad9d76 · e33ccfab
Commit e33ccfab authored 11 months ago by T. van der Sar
--- a/docs/7_tight_binding.md
+++ b/docs/7_tight_binding.md
@@ -354,7 +354,7 @@ $$ E = E_0 - 2t \cos(ka), $$
 we get

 $$
-ka = \pm\arccos[(E - E_0) / 2t],
+ka = \pm\arccos[-(E - E_0) / 2t],
 $$

 and