2.3 textbook

[Yan Zhou]

I am quite confused about the value of $2+sin\theta$. We know $sin\theta = \frac{1}{2i}(z - \frac{1}{z})$,
it says that $2 + sin\theta = 2 +(\frac{1}{2}i)(z-\frac{1}{z})$. Is that a typo?

[Victor Ivrii]

Yes, wrong sign  in the middle (should be $\drac{1}{2i}=-\dfrac{i}{2}$) but the final result is correct