Subjective synonymy
¥SynS(A, B, C) Ñ C as point of view
¥ SynS(A, B, C) = D(C-A, C-B)
¥
¥0 £ SynS(A, B, C) £  p
¥normalization: 
¥0 £ asin(sin(SynS(A, B, C))) £  p/2
¥
a
B
A
C
CÕ
CÓ
aÕ
aÓ