已知P是△ABC内一点,且满足向量PA+2PB+3PC=0,记△ABP,△
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已知P是△ABC内一点,且满足向量PA+2PB+3PC=0,记△ABP,△
BCP,△ACP的面积依次为S1.S2.S3,则它们之比为?
BCP,△ACP的面积依次为S1.S2.S3,则它们之比为?
PA+2PB+3PC=0
(PA+2PB+3PC)xPA=0xPA (x :cross product )
2PBxPA+3PCxPA=0
2|PBxPA|=3|PCxPA|
S1=(3/2)S3 (1)
also
PA+2PB+3PC=0
(PA+2PB+3PC)xPB=0
|PAxPB|=3|PCxPB|
S1=3S2 (2)
from (1) ,(2)
S1:S2:S3= 1:3:3/2=2:6:3
再问: 出错了,检查,没有这个选项啊...
再答: PA+2PB+3PC=0 (PA+2PB+3PC)xPA=0xPA (x : cross product ) 2PBxPA+3PCxPA=0 2|PBxPA|=3|PCxPA| S3=(2/3)S1 (1) also PA+2PB+3PC=0 (PA+2PB+3PC)xPB=0 |PAxPB|=3|PCxPB| S2=(1/3)S1 (2) from (1) ,(2) S1:S2:S3= 1:1/3: 2/3=3:1:2
(PA+2PB+3PC)xPA=0xPA (x :cross product )
2PBxPA+3PCxPA=0
2|PBxPA|=3|PCxPA|
S1=(3/2)S3 (1)
also
PA+2PB+3PC=0
(PA+2PB+3PC)xPB=0
|PAxPB|=3|PCxPB|
S1=3S2 (2)
from (1) ,(2)
S1:S2:S3= 1:3:3/2=2:6:3
再问: 出错了,检查,没有这个选项啊...
再答: PA+2PB+3PC=0 (PA+2PB+3PC)xPA=0xPA (x : cross product ) 2PBxPA+3PCxPA=0 2|PBxPA|=3|PCxPA| S3=(2/3)S1 (1) also PA+2PB+3PC=0 (PA+2PB+3PC)xPB=0 |PAxPB|=3|PCxPB| S2=(1/3)S1 (2) from (1) ,(2) S1:S2:S3= 1:1/3: 2/3=3:1:2
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