# stuck at the middle of the differential part

• Nov 8th 2008, 01:24 PM
yzc717
stuck at the middle of the differential part
• Nov 8th 2008, 04:50 PM
vincisonfire
$\frac{dG}{dx} = \frac{\partial G}{\partial x}\frac{\partial x}{\partial x}+\frac{\partial G}{\partial y}\frac{\partial y}{\partial x} +\frac{\partial G}{\partial Z}\frac{\partial Z}{\partial x}$

$0 = \frac{\partial G}{\partial x}\cdot 1+\frac{\partial G}{\partial y}\cdot 0 +\frac{\partial G}{\partial Z}\frac{\partial Z}{\partial x}$

$- \frac{\partial G}{\partial x}=\frac{\partial G}{\partial Z}\frac{\partial Z}{\partial x}$

$\frac{- \frac{\partial G}{\partial x}}{\frac{\partial G}{\partial Z}}=\frac{\partial Z}{\partial x}$
• Nov 8th 2008, 05:08 PM
vincisonfire
$
\frac{dG}{dx} = \frac{\partial G}{\partial x}\frac{\partial x}{\partial x}+\frac{\partial G}{\partial y}\frac{\partial y}{\partial x} +\frac{\partial G}{\partial z}\frac{\partial z}{\partial x}
$

$
0 = \frac{\partial G}{\partial x}\cdot 0+\frac{\partial G}{\partial y}\frac{\partial y}{\partial x} +\frac{\partial G}{\partial z}\frac{\partial z}{\partial x}
$

$
\frac{- \frac{\partial G}{\partial x}}{\frac{\partial G}{\partial y}}=\frac{\partial y}{\partial x}
$

Similarly
$
\frac{- \frac{\partial G}{\partial y}}{\frac{\partial G}{\partial z}}=\frac{\partial z}{\partial y}
$

$
\frac{- \frac{\partial G}{\partial z}}{\frac{\partial G}{\partial x}}=\frac{\partial x}{\partial z}
$

$
\frac{- \frac{\partial G}{\partial x}}{\frac{\partial G}{\partial y}}\cdot \frac{- \frac{\partial G}{\partial y}}{\frac{\partial G}{\partial z}} \cdot \frac{- \frac{\partial G}{\partial z}}{\frac{\partial G}{\partial x}}=-1
$

See that each term at the numerator eliminates with one at the denominator.
• Nov 8th 2008, 05:47 PM
yzc717
Quote:

Originally Posted by vincisonfire
$
\frac{dG}{dx} = \frac{\partial G}{\partial x}\frac{\partial x}{\partial x}+\frac{\partial G}{\partial y}\frac{\partial y}{\partial x} +\frac{\partial G}{\partial z}\frac{\partial z}{\partial x}
$

$
0 = \frac{\partial G}{\partial x}\cdot 0+\frac{\partial G}{\partial y}\frac{\partial y}{\partial x} +\frac{\partial G}{\partial z}\frac{\partial Z}{\partial x}
$

$
\frac{- \frac{\partial G}{\partial x}}{\frac{\partial G}{\partial y}}=\frac{\partial y}{\partial x}
$

Similarly
$
\frac{- \frac{\partial G}{\partial y}}{\frac{\partial G}{\partial z}}=\frac{\partial z}{\partial y}
$

$
\frac{- \frac{\partial G}{\partial z}}{\frac{\partial G}{\partial x}}=\frac{\partial x}{\partial z}
$

$
\frac{- \frac{\partial G}{\partial x}}{\frac{\partial G}{\partial y}}\cdot \frac{- \frac{\partial G}{\partial y}}{\frac{\partial G}{\partial z}} \cdot \frac{- \frac{\partial G}{\partial z}}{\frac{\partial G}{\partial x}}=-1
$

See that each term at the numerator eliminates with one at the denominator.

Thanks so much, I am still working on it myself, see what i got wrong through the solutuion you gave me.

I just having a hard time on differential equation with multi-variables