AC//A1C1
A1B//CD1
面A1BC1//面ACD1
AD1在面ACD1上,A1C1在面A1BC1上
异面直线AD1与A1C1的距离即面ACD1与面A1BC1的距离.
B1D⊥AC,B1D⊥AD1
B1D⊥面AD1C,记交点于E
B1D⊥面A1BC1,记交点于F
EF即为两平面间距离
1/2AD1*DD1*DC=1/2AC*AD1*sin60*DE
DE=√3/3
B1F=DE=√3/3
EF=B1D-2DE=√3/3
其实这种题不需要作出公垂线