b

a

afbfdxxf )()()('

CR

QdyPdxdAyP

xQ

a)

b)

C

ydyydxx 24 2

jdrdyi

drdxT

jdrdxi

drdyn

jyxQiyxPyxF

),(),(),(

R

C

C C

dAyQ

xP

PdyQdx

drjdrdxi

drdyjQiPdrnF

)(

)(

1)

dxdyyP

R

dxdyxQ

R

)()(,, xfyxgbxayxS

4321 CCCCC

2) dyyxdxxyx )3()2( 22

C

dyxxdxxxy )()2( 22

C

dyyxdxyx )32()43(