1. The problem statement, all variables and given/known data a) f(x,y)=√ [1−(x2+y2)] b) f(x,y)=2cos(4x+y2) 3. The attempt at a solution a) The domain is such that x2 + y2 must not be greater than 1 In other words, this is expressed (as stated as an option on the answer sheet) as "xy-plane without the line x=y" Why is this so? b) the equation f(x,y)=2cos(4x+y2) has a range of [-2,2] As for the domain, for f(x,y)=2cos(4x+y2) to have a range of [-2,2], (4x +y2 must be 0 or π. How do I express the domain in terms of x and y? The domain for (b) as provided by the answer is R2(xy-plane).