问题 填空题
已知向量
a
b
满足|
a
|=
5
,|
b
|=
13
cos<
a
b
>=
65
65
.若k
a
+
b
a
-3
b
垂直,则k=______.
答案

k

a
+
b
a
-3
b
垂直,

(k

a
+
b
)•(
a
-3
b
)=0

化简可得k

a
2+(1-3k)
a
b
-3
b
2
=0,

代入可得5k+(1-3k)

5
13
65
65
-3×13=0

化简可得解得k=19

故答案为:19

完形填空
完形填空。
    What is a museum? A museum is a good place to keep     1    and beautiful things. A museum may be
a place to learn about science. A museum can be a place     2    art of humans or animals. What is inside
a museum? Some museums     3     old cars and airplanes.     4     museums have pictures and sculptures. Others have rocks and old bones.  One museum even has      5    coal mine inside! Many cities have
museums. Some very small     6    have museums,     7    . Indianapolis has a     8     museum. Children
do not have to     9    to get in. Children often go to the museum. They like to see at the dinosaur bones.
They see a white bear ten feel tall. They go inside an old log cabin(小木屋). On Saturday, Indianapolis
children can     10   talks about animals and trees.
( )1. A. new  
( )2. A. for  
( )3. A. has  
( )4. A. Bit  
( )5. A. the  
( )6. A. homes
( )7. A. too  
( )8. A. adults
( )9. A. pay  
( )10. A. sing
B. old      
B. in      
B. have    
B. A little
B. an      
B. towns    
B. also    
B. people’s
B. speak    
B. see      
C. good        
C. about        
C. there is    
C. Much        
C. a            
C. villages    
C. either      
C. children’s
C. run          
C. hear        
D. important  
D. on        
D. there are  
D. Many      
D. /                                 
D. countries  
D. neither    
D. boy’s  
D. cry        
D. feel      
填空题