Multivariable limit .... no L'Hopital rule? I am looking a bit at limits for multivariable functions by myself, and I can't figure it out; my book only mentions them shortly, but now I am looking at an "assignments for those interested" and it says 
$$\lim_{(x,y) \to (0,0)} \frac{\sin(xy)}{xy} \cos(x+y)$$
But that's a $0$ over $0$ expression... ? 
Do we have a L'Hopital rule for these types of functions? How would I solve it? 

$$\lim_{t\to0}\frac{\sin t}t=1\qquad\lim_{t\to0}\cos t=1\qquad\lim_{(x,y)\to(0,0)}xy=\lim_{(x,y)\to(0,0)}(x+y)=0$$
