y = 3cos$\theta$ + 5 $\left( {\sin \theta {{\sqrt 3 } \over 2} - \cos \theta {1 \over 2}} \right)$ ${{5\sqrt 3 } \over 2}$ sin$\theta$ + ${1 \over 2}$cos$\theta$ y max = $\sqrt {{{75} \over 4} + {1 \over 4}}$ = $\sqrt {19}$