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问题 填空题
已知△ABC的三边分别是a、b、c，且面积S=
a2+b2-c2
4
，则角C=______．
答案

由题意，S=

a2+b2-c2
4
=
2abcosC
4
=
abcosC
2

∵S=

absinC
2

∴cosC=sinC

∵C是△ABC的内角

∴C=45°

故答案为：45°

判断题

人类文明最直接、最集中的传递是在学校的师生之间进行的。[ ]
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补全对话，情景问答
从Ⅱ栏中选出Ⅰ栏中各句的应答语。

Ⅰ
(   )1. What does your father do?          
(   )2. What do you think of the fish?     
(   )3. Do you want to play the guitar with me?
(   )4. What does your brother look like?    
(   )5. Why not go for a picnic with us?    

Ⅱ
A. It’s nice.                 
B. He’s short.               
C. He is a doctor.            
D. Yes, I do.                   
E. Good idea. Let’s go.      
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