已知，Rt△ABC中的两个直角边a，b分别是关于x的方程x2-
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由题意知a+b=
，ab=k．2
∵sinA+sinB=
．2
∴
+a c
=b c
，2
=a+b a2+b2
．2
∴
=a+b (a+b)2-ab
=2 (
)2-2k2
．2
解得k=
．1 2
代入原方程得x2-.
x+2
=0．1 2
∵△=2-2=0．
∴a=b=
．2 2
所以∠A=45°．
| 阅读下面短文，从短文后所给各题的四个选项(A、B、C、D)中，选出可以填入空白处的最佳选项。 | ||||
| The Class 1, Grade 7 students are having a fashion show in the school hall. They are having the show because they want to 1 for Project Hope. Today they are going to 2 you clothes from different times. At the very beginning, Kitty is wearing popular clothes 3 — a white skirt and a pair of white boots. Then Simon has white trousers, and a purple shirt 4 a yellow and red tie. He looks very colorful. Next 5 Amy, cool and young. She is 6 a yellow blouse and a pair of blue jeans both made of cotton. Look, 7 Sandy is! She is wearing a black wool skirt, long red leather boots and a red silk blouse. Her straight long hair is such a popular 8 for school girls, 9 , Daniel walks on as a smart and modern boy, His sport clothes are blue and yellow. He is also wearing 10 trainers, I think they are very comfortable and they are young people's favorite kind of shoes. Do you enjoy the fashion show? Please help them raise money for poor students. | ||||
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