Determine fay when f(x, y) = 2x tan-¹(ry). 1. fay 2. fry 3. fry 4. fxy 5. fxy 6. fxy = = 2xy 1+x²y² 4x (1 + x²y²)² 4y (1 + x²y²)² 2y 1+x²y² 4x (1 + x²y²)² 2xy 1+x²y²