31(a1+bx+c;y) L=.(a,+bx+cy AAPik △Pjk 2△ (ak +b x+cy) △ii 2△ 6, Ckx 2△ k x. xRL (a, +bx+cy) i,j,k=1,2,3 2△ ai=xi-yjXk Vik txkj i k y x P Pij Pik Pjk ( y) 2 1 i i i i L a + b x + c  = i j k j k a = x y − y x i j k b = y − y i j k c = −x + x i, j, k =1,2,3 ( y) 2 1 i i i i L a + b x + c  = ( y) 2 1 j j j j L a + b x + c  = ( y) 2 1 k k k k L a + b x + c  =                      =           y x a b c a b c a b c L L L k k k j j j i i i k j i 1 2 1                     =           k j i i j k i j k L L L y y y x x x y x 1 1 1 1