Homework Help: Partial Derivatives

Spectre32 · Oct 7, 2004

Partial Derivatives of this(respect to x,y).

Code (Text):

Z = (x+y) Sec(xy).

Would my first move be to multiply the

Code (Text):

(x+y)

tot he other side? If so I'm algerba is a bit sketchy :uhh: , how would it be done.

faust9 · Oct 7, 2004

You can algebraically expand the quantity (x+y), or you can use the product rule for derivatives. Either method will get you the result. I'd keep it the way it is personally because if you expand the quantity you'll have to use the product rule twice.

Good luck.

Spectre32 · Oct 7, 2004

Ok so would I get something like this:

[(x+y)+((sin(xy)*y)/(cos(xy)^2))] - [(1+y)+sec(xy)] ??

faust9 · Oct 7, 2004

No, how did you get that? Laptop battery almost dead so I'll not respond to this until later tonight BTW. When doing a partial w/ respect to x, y becomes a constant and vice versa.

Do this: (x+1)sec ((1)(x))d/dx

What would that look like?

Spectre32 · Oct 7, 2004

(cos(x) * (x+1)*sin(x))/(Cos(x)^2)

Spectre32 · Oct 7, 2004

Whoops.... Now I see what I did wrong... wow i'm retarded. I forgot to go through and Differentate Y and then figure it out. But I still think I did it wrong. Sec[x] + (1 + x) Sec[x] Tan[x]