问题
选择题
空间四边形OABC中,OB=OC,∠AOB=∠AOC=
|
答案
∵OB=OC,
cos<
,OA
>=BC
=
•OA BC |
||OA
|BC
=
•(OA
-OC
)OB |
||OA
|BC
=0,|
||OA
|cosOC
-|π 3
||OA
|cosOB π 3 |
||OA
|BC
故选 D.
空间四边形OABC中,OB=OC,∠AOB=∠AOC=
|
∵OB=OC,
cos<
,OA
>=BC
=
•OA BC |
||OA
|BC
=
•(OA
-OC
)OB |
||OA
|BC
=0,|
||OA
|cosOC
-|π 3
||OA
|cosOB π 3 |
||OA
|BC
故选 D.