1
BC=(1,-1,5)-(-2,1,6)=(3,-2,-1)
BC的单位向量:BC0=BC/|BC|=(3,-2,-1)/√14
AP∥BC,且:|AP|=2√14
故:AP=±|AP|*BC0
=(6,-4,-2)或(-6,4,2)
令P点(x,y,z)
即:AP=(x,y,z)-(0,2,3)=(x,y-2,z-3)
故:(x,y-2,z-3)=(6,-4,-2)或:
(x,y-2,z-3)=(-6,4,2)
即:P点(6,-2,1)或(-6,6,5)
2
AB=(-2,1,6)-(0,2,3)=(-2,-1,3)
AC=(1,-1,5)-(0,2,3)=(1,-3,2)
| i j k |
AB×AC= | -2 -1 3 |=-2i+3j+6k+k+9i+4j=7i+7j+7k=(7,7,7)
| 1 -3 2 |
以AB,AC为邻边的平行四边形的面积:
S=|AB×AC|=|(7,7,7)|=√(49*3)=7√3