如图.△ABC中.∠ABC的角平分线与∠ACB的外角∠ACD的平分线交于A1.(1)当∠A为70°时.则∵∠ACD-∠ABD=∠ .∴∠ACD-∠ABD= °∵BA1.CA1是∠ABC的——青夏教育精英家教网——

如图，△ABC中，∠ABC的角平分线与∠ACB的外角∠ACD的平分线交于A₁.

（1）当∠A为70°时，则
∵∠ACD-∠ABD=∠ ，
∴∠ACD-∠ABD= °
∵BA₁、CA₁是∠ABC的角平分线与∠ACB的外角∠ACD的平分线
∴∠A₁CD-∠A₁BD=

（∠ACD-∠ABD）
∴∠A1= °。
（2）根据中的计算结果写出∠A与∠A1之间等量关系。

如图所示，直线a，b被直线c所截，且∠1+∠2=180°，直线a与直线b平行吗？为什
么？

如图所示,将△ABC沿EF折叠,使点C落到点C′处,试探求∠1,∠2与∠C的关系.

如图所示,直角坐标系中，△ABC的顶点都在网格点上，其中C点坐标为（1，2）.

【小题1】写出点A、B的坐标；
【小题2】将△ABC先向左平移2个单位长度，再向上平移1个单位长度，得到△A′B′C′，分别写出△A′B′C′的三个顶点坐标；

如图，已知AD⊥AB，DE平分∠ADC，CE平分∠BCD，且∠1+∠2＝90°，那么BC⊥AB，说明理由。

如图所示，在平面直角坐标系xOy中，A（-1，5），B（-1，0），C（-4，3）.

【小题1】求出△ABC的面积；
【小题2】在图中作出△ABC关于y轴的对称图形△A₁B₁C₁；
【小题3】写出点A₁，B₁，C₁的坐标.

下列选项中表示的数，哪一个是整数（　　）

若方程x²=m的解是有理数，则实数m不能取下列四个数中的（　　）

大课间活动在我市各校蓬勃开展．某班大课间活动抽查了20名学生每分钟跳绳次
数，获得如下数据（单位：次）：50，63，77，83，87，88，89，91，93，100，102，111，
117，121，130，133，146，158，177，188．则跳绳次数在90～110这一组的频率是（　　）

阅读下面短文，根据所给语境，按要求完成下列各题。
Mozart was born on January 27, 1756 and died on December 5 , 1791. When he was three, he often had lessons with his elder sister. （1）His father took him through many different countries, where he played music for lots of people.
But some people didn’t believe a little boy could write such beautiful music. They asked him to stay in a room all by himself for a week and somebody watched the room all the time .（2） In a week , he finished a new piece of music . After that, people believed that he could write beautiful music.
Mozart died when he was still a young man. During his short life he studied music and taught music and played music and wrote music. Even by working so hard, he couldn’t make much money . Often he had to borrow money from his friends. But his music made him happy and for more than two hundred years his music has made other people happy, too.
【小题1】将（1）处翻译成汉语。
___________________________________________________________________________
【小题2】对（2）处黑体部分提问。
___________________________________________________________________________
【小题3】根据短文内容，完成下面的句子。（每空一词）
Mozart was a __________ talent（天才）,but he still lived a ________ life.

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