A C B 十 十 B 2 B 十 P r P P P A x B J1 A 2 +B2+C2√A2+B2+C 42 + B 十 C Axo t Byo +c2 A B y 十 B C      + + + + + + = 2 2 2 2 2 2 2 2 2 0 , , A B C C A B C B A B C A n 0 Pr jnP1P0 = P1P0  n 2 2 2 0 1 2 2 2 0 1 2 2 2 0 1 ( ) ( ) ( ) A B C C z z A B C B y y A B C A x x + + − + + + − + + + − = , ( ) 2 2 2 0 0 0 1 1 1 A B C Ax By Cz Ax By Cz + + + + − + + =