已知兩點
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,
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為坐標原點,若

,則實數(shù)t的值為( )
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知

中,

,點

為
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邊所在直線上的一個動點,則

滿足
A.最大值為16 | B.最小值為4 |
C.為定值8 | D.與 的位置有關(guān) |
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
過點
Q 
作圓
C:
x2+
y2=
r2(

)的切線,切點為
D,且
QD=4.
(1)求
r的值;
(2)設(shè)
P是圓
C上位于第一象限內(nèi)的任意一點,過點
P作圓
C的切線
l,且
l交
x軸于點
A,交
y 軸于點
B,設(shè)

,求

的最小值(
O為坐標原點).
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
三角形的內(nèi)角平分線定理是這樣敘述的:三角形一個內(nèi)角的平分線分對邊所成的兩條線段與這個角的兩邊對應(yīng)成比例。已知在
△ABC中,∠
A=60
o,∠
A的平分線
AD交邊
BC于點
D,設(shè)
AB=3,且

,則
AD的長為( )
A.2 | B. | C.1 | D.3 |
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科目:高中數(shù)學(xué)
來源:不詳
題型:填空題
已知△

內(nèi)接于以

為圓心,1為半徑的圓,且

,則

________
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科目:高中數(shù)學(xué)
來源:不詳
題型:單選題
已知一正方形,其頂點依次為

,平面上任取一點

,設(shè)

關(guān)于

的對稱點為

,

關(guān)于

的對稱點為

,……,

關(guān)于

的對稱點為

,則向量

等于
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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
(本小題12分)已知向量

.
(1)若

‖

,求

;
(2)當

時,求

的最值。

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科目:高中數(shù)學(xué)
來源:不詳
題型:解答題
.已知平行四邊形ABCD中,


,


, M為AB中點,N為BD靠近B的三等分點.
(1)用基底

,

表示向量

,

;
(2)求證:M、N、C三點共線.

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科目:高中數(shù)學(xué)
來源:不詳
題型:填空題
已知點P是△ABC的中位線EF上任意一點,且EF//BC,實數(shù)x,y滿足

。設(shè)△ABC,△PBC,△PCA,△PAB的面積分別為S,S
1,S
2,S
3,記

取最大值時,

的值為__________
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