functions

z1 = sin((x^2)-2 (y^2)) 
z2 = ln((x^2)-2 (y^2))
z3 = (e^((x^2)-2 (y^2)))
z4 = (x^2)-2 (y^2)
z5 = (1/((x^2)-2 (y^2)))

3D plots

3D plot # 1

3D plot # 2

3D plot # 3

3D plot # 4

3D plot # 5

contour plots

contour plot # 1

contour plot # 2

contour plot # 3

contour plot # 4

contour plot # 5