问题 选择题
已知△ABC的三内角A、B、C满足条件
sin2A-(sinB-sinC)2
sinBsinC
=1
,则角A等于(  )
A.30°B.60°C.70°D.120°
答案

sin2A-(sinB-sinC)2
sinBsinC
=1,

a2-(b-c)2
bc
=1

即b2+c2-a2=bc

根据余弦定理得cosA=

b2+c2-a2
2bc
=
1
2

A∈(0,180°)

∠A=60°

故选B.

简答题

黄某在小学和初中期间经常欺负小同学,勒索小同学少量财务,因而多次受到老师的批评。高二时自行辍学,放弃了学业。走上社会后,他不务正业,曾因打架斗殴、小偷小摸等行为被公安机关罚款、拘留多次,但他仍不思悔改,后又作案20多起,最终被人民法院以流氓罪、诈骗罪、抢劫罪、盗窃罪判处无期徒刑,剥夺政治权利终身。

⑴、黄某不同阶段所受惩处的性质一样吗?说明理由。(6分)

                                                                       

                                                                       

                                                                       

⑵、在人民法院给予黄某的刑罚中,哪个属于主刑?哪个属于附加刑?(4分)

                                                                       

                                                                       

⑶、根据刑法的规定,我国刑罚中的附加刑包括哪几种?(4分)

                                                                       

                                                                       

⑷、黄某从一般违法走上犯罪道路的过程告诫我们,如何才能成为一个合格的现代公民?(6分)

                                                                       

                                                                       

                                                                       

                                                                       

单项选择题