第二节One possible versionI asked him, "Why did you not tell my roommate that youare my brother?"He replied with a smile," If so, they willmake fun of you for having such a brother and you 'll surely feelembarrassed."Hearing his words I felt so touched that tears filledmy eyes. Then he took out some money from his pocket and put itin my hand, telling me to mind my health and not to worry abouthim. I pulled my brother into my arms and burst out crying. Thatyear, my brother was 20 years old and I was 23Several years later, when my brother got married, he wasasked who was the person he loved most. Without a secondthought, he answered, "My sister. " Then he continued, One day,my parents happened to be out and I became seriously ill. It wasmy sister who took me immediately to the hospital and finally Irecovered. From that day on, I was determined to do all that I couldfor my sister because I thought she was the dearest person to me.On such an occasion, I was moved to tears again by what he saidand took great pride in having such a nice brother

18向预测……解三角形是全国卷高考中与数列轮流出现的常考题目,通常以正余弦定理为工具,计算三角形的未知的边角和三角形面积,通常与三角恒等变换结合考查思路……1)用正弦定理化边为角,进行三角恒等变换,求得角C的余弦得角;(2)由面积公式及余弦定理建立关于一的三角表达式,解关于一的二次方程求值参考答案…1)由已知及正弦定理得sinB=2 sin Ccos e-2sinA,(2分)sin b=2sin Ccos B-2sin Ccos B-2cos Csin B化简得sinB=-2 cos Csin B又sinB≠0又C∈(0,π∴C=-“.(6分)(2)由S=c2,得 absin C=c2,即c2=5ab,(8分)根据余弦定理c2=a2+b2-2 abcs C,得c2=a2+b+ab=5ab即a2+b2-4ab=0,(10分)两边同除以b,可得(台)-4×+1解得=2+√3或=2-√3.(12分)

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