i am graphing objects by using level sets (setting z=a constant) and sections (setting x and y = a constant)

i have to sketch..

1.) f (x,y)= -2

2.) g(x,y)= cosy

3.) h(x,y)= 1-x

any pointers/hints on how to do any of these? the first one doesn't have x or y so i wasn't sure what to do..thanks