we have the following:
[tex]\begin{gathered} y=-\frac{1}{2}\cos (\frac{3}{2}x) \\ x=0 \\ y=-\frac{1}{2}\cos (\frac{3}{2}\cdot0) \\ y=-\frac{1}{2}\cos (0)=-\frac{1}{2}\cdot1 \\ y=-\frac{1}{2} \\ (0,-\frac{1}{2}) \end{gathered}[/tex]therefore, the y-intercept is (0, -1/2)