how to implement cartesian coordinates

I have a image

http://imgur.com/EOyLRe6

which consists of cartesian coordinates,plz tell how to implement these coordinates,which function must be used

Kindly help

[Walter Roberson]

What is the context for that? It does not appear to be general Cartesian coordinates: it appears to be the expression in Cartesian coordinates of something like a wave function or a rotation.

[kash]

it is equation taken from

http://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations

which is Navier–Stokes equations

[kash]

its for fluid flow

Answer 1

[Walter Roberson]

Use the symbolic toolbox function diff()

[kash]

walter tried example1 in

http://www.mathworks.in/help/symbolic/mupad_ref/diff.html

i got error as

Undefined function or variable 'x'.

when i gave x=2

i got

ans =

     []

y i get such answer

[kash]

i tried syms x and got answer

syms x
f=x^3
p=diff(f)
a=subs(f,[x],2)

i got answer

p =

3*x^2

a =

     8

a must be 12,why i get 8

[Walter Roberson]

8 is correct. f = x^3, and 2^3 is 8.

[kash]

after differentation we get 3x^2,so the answer should be 12 rite

[Walter Roberson]

No, the answer for a=subs(f,[x],2) should be 8. Calculating diff(f) makes no difference to the value you find by substituting something into f.