题目

.求值：tan 20°+tan 40°+tan 20°tan 40°= . 答案：【解析】因为tan 60°=tan(20°+40°)==， 所以tan 20°+tan 40°=-tan 20°tan 40°， 所以tan 20°+tan 40°+tan 20°tan 40°=. 从方框中选出能填入对话空白处的相应句子, 有两个多余选项。 A: Hi, Jack! Where did you go on vacation last weekend? B: I went to Yichang with my parents． A: Yichang? It’s a lot far from here．   1    B: We went there by plane． A: How was your trip?   2    B: Of course I did．I visited the Great Dam．It is great． A:   3   ． B: It was sunny．The sunshine was so beautiful． A:   4    B: Oh, it was delicious．I liked it very much．  A：  5    B: They were very friendly．They wear their national costumes（服装）．Their clothes are very beautiful．And many of them are good at singing． B: Well, I hope to go there some day． A． How was the food there? B． Who went there with you? C． How did you go there? D． What did you see there? E． What do you think of the people there? F． How was the weather? G． Did you have a good time?