(1) (1 + 3) ÷ 2 = 2(2 + 4) ÷ 2 = 3所以 用(2 , 3)表示点C(2)(x1 + x2) ÷ 2 = (x1 + x2)/2(y1 + y2) ÷ 2 = (y1 + y2)/2所以 用( (x1 +x2)/2 , (y1 + y2)/2 ) 表示点C
1)C[(1+3)/2,(2+4)/2],即C(2,3)2)C[(x1+x2)/2,(y1+y2)/2]
(X3,Y3)