∵∠BAC=
π
2,∴
AB•
AC=0,
∵z1=[7i−1/1+i]=3+4i,对应点(3,4),z2=0,对应点(0,0),z3=(c,c-6),
∴(-3,-4)•(c-3,c-6-4)=0,-3(c-3)+(-4)(c-10)=0,7c=49,
∴c=7.
故答案为 7.
∵∠BAC=
π
2,∴
AB•
AC=0,
∵z1=[7i−1/1+i]=3+4i,对应点(3,4),z2=0,对应点(0,0),z3=(c,c-6),
∴(-3,-4)•(c-3,c-6-4)=0,-3(c-3)+(-4)(c-10)=0,7c=49,
∴c=7.
故答案为 7.