Fix notes typo (Thanks to Mert Hidayetoglu)

doc/.gitignore

+*converted-to*pdf
+out

doc/expansion-notes.tex

@@ -108,6 +108,6 @@ The translated coefficients satisfy
 %
 \[ H_k^{(1)}(|s - c_2|) e^{i k \theta_{sc_2}} = (-1)^k \sum_{l = -\infty}^{\infty}
 \underbrace{J_l(|s - c_1|) e^{- i l \theta_{sc_1}}}_{\textrm{old coefficients}}
-H_{k + l}^{(1)}(|c_1 - c_2|) e^{(k + l)\theta_{c_2c_1}}. \]
+H_{k + l}^{(1)}(|c_1 - c_2|) e^{i(k + l)\theta_{c_2c_1}}. \]
 
 \end{document}