问题
解答题
求证：2sin（
|
答案
证明：左边=2sin（
-x）•sin（π 4
+x）π 4
=2sin（
-x）•cos（π 4
-x）…（4分）π 4
=sin（
-2x） …（8分）π 2
=cos2x …（12分）
=右边，
原题得证．…（13分）
搜题请搜索小程序“爱下问搜题”
求证：2sin（
|
证明：左边=2sin（
-x）•sin（π 4
+x）π 4
=2sin（
-x）•cos（π 4
-x）…（4分）π 4
=sin（
-2x） …（8分）π 2
=cos2x …（12分）
=右边，
原题得证．…（13分）
| 完形填空。 | ||||
| Maria Gomez was born in Peru (秘鲁). She grew up in a small village. She went to school when she was six years old. She went to an elementary school (小学), but she didn't 1 to high school. Her family was very 2 and she had to go to work when she was thirteen years old. She worked in a shoe factory. When Maria was seventeen years old, her family 3 to the United States. First they lied in Los Angeles, and then they moved to San Francisco. When Maria 4 to the United States, she was not very happy. She missed her friends in Peru, and she couldn't 5 a word of English. She began to study English at night, 6 work in a factory during the day. Maria studied very hard, and now she speaks English well. She's 7 at night, but now she's studying typing. She wants to 8 a secretary (秘书). Maria still misses her friends in Peru. But she's very happy now, and she hopes she will have a good future in the new country. | ||||
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