# HELP in differential calculus

• Apr 2nd 2009, 02:03 PM
amyna
HELP in differential calculus
hey,I have 2 questions that I need help in .

1)If U=tan^-1(x^3+y^3/x-y)Prove that x*du/dx + y*du/dy = Sin2U

2)d^2u/2x*dy=d^2u/dx*dy wen U=log(x^2+y^2/xy)

• Apr 3rd 2009, 04:27 PM
stapel
How does "U" relate to "u"? What did you find when you took the various derivatives?

Please be complete. Thank you! :D
• Apr 5th 2009, 03:32 AM
amyna
I think 'U' and 'u' are the same thing ??? Does that make any sense ?

Although,
1)If U=tan^-1(x^3+y^3/x-y)Prove that x*du/dx + y*du/dy = Sin2U

this has something to do iwth Partial derivatives

2)d^2u/2x*dy=d^2u/dx*dy wen U=log(x^2+y^2/xy)

and this has something to do with Successive Partial Derivatives

Well, honestly i am totally pathetic at this calculus so I have no clue at all (Giggle) It was an assignment question and the lecturer refuses to tell us how to do it ..Until we hand it in and obviously get it wrong ...

Okay,sorry for goin into the history of pointless things ...I'm sure u dont rely care (Wink)

THANK YOU EVA SO MUCH (Happy)