问题
填空题
已知点A、B、C满足
|
答案
∵
=3,|AB|
=4,|BC|
=5|CA|
∴
2+|AB|
2=|BC|
2|CA|
∴
⊥AB BC
∴
•AB
+BC
•BC
+CA
•CA
=AB
•BC
+CA
•CA
=AB
•(CA
+AB
)=-BC
2=-25CA
故答案为-25
已知点A、B、C满足
|
∵
=3,|AB|
=4,|BC|
=5|CA|
∴
2+|AB|
2=|BC|
2|CA|
∴
⊥AB BC
∴
•AB
+BC
•BC
+CA
•CA
=AB
•BC
+CA
•CA
=AB
•(CA
+AB
)=-BC
2=-25CA
故答案为-25