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Nonlinear Control Sy.. - Free

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A.1. CHAPTER 3<br />

is symmetric.<br />

Proof: To prove necessity, we assume that g(x) = VV(x). Thus<br />

Thus<br />

and the result follows since<br />

T=<br />

av<br />

a2v a2v a2v<br />

x xl<br />

717a'2v acv o vv<br />

2 x2 x2 TX. X2<br />

I<br />

L<br />

a2v<br />

x<br />

a2v<br />

z2 x<br />

a2v<br />

xn x, J<br />

a2v<br />

=<br />

a2v To rove sufficiency, assume that<br />

TX-1 xI<br />

x; xl<br />

'99i 0g<br />

axe au<br />

and consider the integration as defined in (3.7):<br />

V (x) =<br />

fox<br />

xl<br />

g(x) dx = f g1(si, 0, 0) ds1<br />

0<br />

X2<br />

+ f g2(xi, s2, 0, ... , 0) ds2 +<br />

0<br />

p Y,<br />

. +<br />

We now compute the partial derivatives of this function:<br />

av<br />

ax-1<br />

gi (xi) o, ... , 0) +fx2<br />

+ 0<br />

x,9g n<br />

X + / 5ag,<br />

axl(xl,x2,...,sn) dsn<br />

10<br />

xn<br />

(x1, s2, 0, ... , 0) ds2 +<br />

X2 a91<br />

91(x1,0)...,0) + J 5x2(x1,s2,0,...,0) ds2 + ...<br />

where we have used the fact that', by assumption. It then follows that<br />

dsn<br />

311<br />

9n(xl,x2,...,sn) dsn(A.5)

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