2-nd type boundary conditions

N

N

i (x, y)

Ui i (x, y)

j (x, y)dS Ui

n

j (x, y)d 0

i 1 S

i 1

N

i (x, y)

~

Replace approximation

~

U

F

Ui

U

U

n

n

by real function:

n

n

2

i 1

If

U

the second term is equal to zero

n 0

b

(x, y)F (x, y)d

N

j

aij Ui bj

j

2

i 1