问题 选择题

在Rt△ABC中,ÐC=90°,若将各边长度都扩大为原来的2倍,则ÐA的正弦值(  )

A.扩大2倍

B.缩小2倍

C.扩大4倍

D.不变

答案

答案:D

根据相似三角形的概念,知若各边长都扩大2倍,则sinA的值不变.故选D.

材料分析题

材料一:郑州女青年杨丽娟曾是优秀学生干部,但初二以后由于追星却走上了辍学追星的迷途。其父母不但不劝阻,反而一度资助,支持女儿,甚至要卖肾筹集路费帮女儿完成追星梦,最后走上不归路。

材料二:电视剧《恰同学少年》的热播,引起了强烈反响。青年时期的毛 * * 就富有遐想和抱负,并产生无私无畏的巨大动力和坚忍不拔的毅力。

(1)材料一中的杨丽娟父母的做法对吗?你认为家长应怎样做?

                                                                                                                                                                

                                                                                                                                                              

(2)结合材料二说明青少年怎样才能使自身价值得到充分实现?

                                                                                                                                                               

                                                                                                                                                              

(3)结合两则材料思考:对待“社会流行”我们的正确态度是什么?

                                                                                                                                                             

                                                                                                                                                              

多项选择题