Find the local maximum and minimum values and saddle point(s) of
the function. If you have three-dimensional graphing software,
graph the function with a domain and viewpoint that reveal all the
important aspects of the function. (Enter your answers as a
comma-separated list. If an answer does not exist, enter DNE.)
1)f(x, y)
= 6y
cos(x), 0 ≤
x ≤ 2π
2)f(x, y) =
y2 − 6y
cos(x), −1 ≤
x ≤ 7
3)f(x, y) = 6 sin(x) sin(y), −π
< x <...