\[
\begin{array}{l}
 \sin x \cdot chy + i\cos x \cdot shy = 0 + i\frac{4}{3} \\ 
 \sin xchy = 0 \\ 
 \cos xshy = \frac{4}{3} \\ 
  \\ 
 \sin x = 0;x = k\pi ;k = 0, \pm 1... \\ 
 \cos k\pi  \cdot shy = \frac{4}{3} \\ 
 shy = \frac{4}{3}( - 1)^k  \\ 
 \frac{{e^y  - e^{ - y} }}{2} = \frac{4}{3}( - 1)^k  \\ 
 \end{array}
\]