Question

Galera alguém pode me ajudar nessa tarefa???

Answer 1

 Oi Micax!!

 Inicialmente, devemos encontrar os ângulos...
 
$\begin{cases}\frac{9\pi}{2}=\frac{8\pi}{2}+\frac{\pi}{2}\\\\\frac{17\pi}{4}=\frac{16\pi}{4}+\frac{\pi}{4}\end{cases}\Rightarrow\begin{cases}\frac{9\pi}{2}=\underbrace{4\pi}_{2\,\;\text{voltas}}+\frac{\pi}{2}\\\\\frac{17\pi}{4}=\underbrace{4\pi}_{2\,\;\text{voltas}}+\frac{\pi}{4}\end{cases}$
 
 Daí,

$y=\frac{\cos90^o-\sin90^o}{\cos45^0+3\cdot\sin45^o}\\\\y=\frac{0-1}{\frac{\sqrt{2}}{2}+\frac{3\sqrt{2}}{2}}\\\\y=\frac{-1}{\frac{4\sqrt{2}}{2}}\\\\y=-\frac{1}{2\sqrt{2}}\times\frac{\sqrt{2}}{\sqrt{2}}\\\\\boxed{y=-\frac{\sqrt{2}}{4}}$