1. The problem statement, all variables and given/known data question asks: lim(x,y) -> (0,0) cos(xy) -1 / [x^2 y^2] 2. Relevant equations 3. The attempt at a solution if you multiply the top and bottom by cos(xy) + 1 you get -[sin^2(xy)/(xy)^2] * [1/cos(xy) + 1] but in the solution they somehow got rid of the denominator (xy)^2, because if that's there the denominator is still 0. How do you get rid of that?