find ∂w/∂r and ∂w/∂s where r =1 and s = -1 if w=(x + y + z)^2

where x = r - s

y = cos (r + s)

z = sin (r + s)

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- Oct 27th 2007, 08:21 AMm777find ∂w/∂r......
find ∂w/∂r and ∂w/∂s where r =1 and s = -1 if w=(x + y + z)^2

where x = r - s

y = cos (r + s)

z = sin (r + s) - Oct 27th 2007, 04:33 PMqyzren
just sub in the expressions for x,y,z.

w = [(r-s) + cos(r+s) + sin(r+s)]²

if you take ∂w/∂r, then you get ∂w/∂r = 2[1 - sin(r+s) + cos(r+s)][(r-s) + cos(r+s) + sin(r+s)]

then just sub in values of r & s.

i'm sure you can do it for ∂w/∂s as well.