题干

已知三棱锥P﹣ABC中,PA=4,AB=AC=2 3 ,BC=6,PA⊥平面ABC,则此三棱锥的外接球的半径为____.
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4

同类题2

阅读《唤醒传统节日的仪式感》,完成下列小题。

唤醒传统节日的仪式感

    ①“前庭后院挂满了灯笼,又是宫灯,又是纱灯,烛光辉煌,地上铺了芝麻秸儿,踩上去咯咯吱吱响。”作家笔下的传统节日仪式,总能勾起许多人的乡愁。在物质丰富、文化多样的今天,尤其需要唤醒传统节日的仪式感。

    ②传统节日的仪式感来自长久流传的节日仪式。过节要有“规定动作”,“过”意味着庄严,“节”代表着主题。例如,欢度春节,我们只有历经如贴春联、穿新衣、守岁、吃饺子、相互拜年、舞狮舞龙等节日仪式,方能获得辞旧迎新、欢乐喜庆、和谐友爱、感恩怀想、憧憬美好等节日仪式感。仪式感犹如生活的调味剂,文化的倍增器,它让潦草的生活变得精致,让平庸的生命变得庄重。元宵观灯的美好祈求,清明祭祖的慎终追远,中秋赏月的千里相思,重阳登高的健康企盼……正是这些节日仪式感的获得,才复苏了我们对民族文化的记忆,涵养着我们对民族文化的情感。

    ③如果没有节日仪式带来的仪式感,诸多的传统节日便会与普通的假期无异。或吃吃喝喝、玩玩闹闹,或埋首于手机、沉迷在网络,不仅没有丝毫的过节气氛,更不能获得一丁点儿的传统节日感受。如果只是贪图舒适享受,把节日仪式当作应景的负担,甚至贴上“糟粕”的标签一脚踢开,这种没有仪式的节日还能称之为传统节日吗?物的败坏尚可恢复,而文化精神一旦败落下去就难以拯救了。

    ④当然,对节日仪式的继承与创新,哪一方面都不能轻视。过去春节放爆竹,如今“燃放”环保的电子爆竹;过去拜年磕头作揖,如今发短信、录视频、传微博……变化的是过节形式,不变的是文化追寻和情感慰藉的节日内涵。“非新无以为进,非旧无以为守。”唤醒仪式感并不仅是发思古之幽情,也不是搞形式主义,而是要找到传统文化和节日内涵的时代载体。如此,传统习俗才能生生不息,传统节日才能叫人回味无穷。

    ⑤传统节日仪式沉淀民族文化,增强民族文化认同感。不论我们走多远,传承好我们的传统节日文化,我们方能记住回家的路。

同类题5

阅读短文,从每小题所给的四个选项中,选出能回答所提问题或完成所给句子的最佳答案。

B

    People often think of the North Pole(北极) and the South Pole as similar frozen(冰冻的) wastelands. They are both places with very cold temperatures and few people live there. However, the North and South Poles are not much alike as people may imagine.

    The North Pole has no land, only thick ice. Temperatures seldom go above 32°F, at which water turns into ice. Most of the time, it stays below zero. In winter temperatures are usually as low as -30°F.

    Although conditions were very poor, people tried for many centuries to reach the North Pole. About 100 years ago, two men, Robert Peary and Mathew Henson, were able to get to this environment full of troubles and difficulties. They reached the North Pole on March 8th, 1909. It was really a hard trip for them.

    There are few things more dangerous than crossing the Arctic(北极圈) on foot. People who stayed there may face many problems: very cold temperatures, sudden storms, and even hunger. Most of the area is uninhabited. Few people can live in such a difficult place.

    People might think that with such low temperatures for most of the year, the ice would be thick and hard. However, this is not true in the Arctic. The movement of the ocean water under the ice may often cause many different changes on the surface. Sometimes the ice breaks into two opening lanes of water(水道) called “leads”. Anyone who falls into a lead can be frozen to death in a few minutes.