问题
选择题
已知A为锐角，tanA=
|
答案
在Rt△ABC中，∠C=90°，则sinA=
，tanA=a c
和a2+b2=c2，a b
由tanA=
知，如果设a=3x，则b=4x，结合a2+b2=c2得c=5x．3 4
∴sinA=
=a c
．3 5
故选A．
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已知A为锐角，tanA=
|
在Rt△ABC中，∠C=90°，则sinA=
，tanA=a c
和a2+b2=c2，a b
由tanA=
知，如果设a=3x，则b=4x，结合a2+b2=c2得c=5x．3 4
∴sinA=
=a c
．3 5
故选A．
| Read and choose. 情景选择！请你选出正确的答案。 |
| 1. 当你想问大家“谁饿了？”时，用英语可以说： |
[ ] |
| A. Are you hungry? B. Who is hungry? C. Who are hungry？ |
| 2. 当你想表达“你想吃些什么呢？”时，你可以用英语说： |
[ ] |
| A. What would you like to eat? B. Would you like some food? C. What you like to eat? |
| 3. 当你想问李明“你在干什么？”时，用英语可以说： |
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| A. What are they doing, Li Ming? B. What are you doing, Li Ming? C. What is he doing, Li Ming? |
| 4. 当你建议朋友吃些香蕉时，可以说： |
[ ] |
| A. Here are some bananas. B. Would you like some bananas? C. Here it is. |
| 5. 如果朋友建议你喝瓶汽水，你不想喝时应说： |
[ ] |
| A. Yes, please. B. Here you are. C. No, thank you. |