Use a computer to graph the function using various domains and viewpoints. Gel a printout of one that, in your opinion, gives a good view. If your software also produces level curves, then plot some contour lines of the same function and compare with the graph.

59. f ( x , y ) = e − ( x 2 + y 2 ) / 3 ( sin ( x 2 ) + cos ( y 2 ) )