題組內容

1. 設 f (x,y)=xy , x(t)=cost , y(t)=sint ,g(t)=f(x(t),y(t)),t ∈ (-∞,∞)

(i) (the gradient vector field of f ) 64cb1df61a2da.jpg=?畫幾條 f 的等高線與一些在其上之64cb1e0c5aaca.jpg.