Consider angles x and y such that[tex]$0 \le y \le x \le \frac\pi2$[/tex] and [tex]$\sin(x+y) = 0.9$[/tex] while [tex]$\sin(x-y) = 0.6$[/tex]. What is the value of
[tex]$(\sin x + \cos x)(\sin y + \cos y)?$[/tex]