só responda se estiver certeza da resposta obrigado
[tex]y=\frac{cos(\frac{9 \pi}{2})-sen(\frac{9 \pi}{2})}{cos(\frac{17 \pi}{4}+3.sen(\frac{17 \pi}{4})}=[/tex]
[tex]y=\frac{0-1}{\frac{\sqrt2}{2}+3.\frac{\sqrt2}{2}}=\frac{-1}{2\sqrt2}=\frac{-\sqrt2}{4}[/tex]
