Math Is Fun Forum

Flowers4Carlos

Member

Registered: 2005-08-25

Posts: 106

unit normal vector

i have a quick question regarding the unit normal vector on the following integral:

∫∫F•dS = ∫∫F•ndS
s             s

if the surface S is given by z=g(x,y) then the unit normal vector is f(x,y,z)= z - g(x,y)  ⇒

       gradf(x,y,z)
n= -----------------
      |gradf(x,y,z)|

my question is if i'm given the surface 3z=g(x,y), then what should the unit normal vector be???

is it f(x,y,z) = 3z - g(x,y)     or     f(x,y,z) = z - g(x,y)/3

Last edited by Flowers4Carlos (2005-12-19 22:21:43)

austin81

Member

Registered: 2005-03-21

Posts: 39

Re: unit normal vector

In my opinion I do think (x,y,z) = [z - g(x,y)]/3 is coorect.Since we shall be integrating

austin81

Member

Registered: 2005-03-21

Posts: 39

Re: unit normal vector

I'm not very sure of that.