几种数学符号的意义及其来历

一、“ 、-、×、÷”的来历“ ”号是在水平面平行的一横上加上垂直的一竖,表示增加的意思。在符号“ ”上去掉一竖成“-”号,表示减少的意思。这个符号的最早使用人是15世纪德国数学家魏德曼。“×”号是18世纪美国数学家欧德来首创,将符号“ ”号倾斜过来,表示几个相同加数连续相加。“÷”号是18世纪瑞士数学家哈纳制定,他是根     

关于学报论文的数学式和反应式

1）文章中重要的或后文将要重新提及的数学式、反应式等可另行起排,并用阿拉伯数字连续编序号（式码）,序号加圆括号,右顶格排出。 2）长数学式超过1行时,应在“=”、“≈”、“<”、“>”等关系符号,或在“ ”、“-”、“×”、“÷”等运算符号处转行,2次以上转行者,应使关系符号和运算号分别对齐。 3）反应式在反应方向符号“→”、“=”、“”等处转行,式中的反应条件就用比正文小1号的字符标注于反应方向符号的上下方。     

数学符号教学：“科学要求”“现实问题”及“优化策略”

基于“精确性与多义性相结合”“具体性与抽象性相统一”“操作性与逻辑性相补充”“文化性与应用性相融通”等数学符号教学的科学要求,探讨了数学符号教学的现实问题：内涵理解不精准、书写格式不规范、表征形式不统一、背景了解不充分、迁移运用不熟练．由此提出了数学符号教学的优化策略：准确理解数学符号内涵,切实感悟数学符号要义;严格规范数学符号书写,全面提高符号学习成效;不断加强语言互译训练,有效建构数学统一表征;适当渗透数学符号文化,助力培养符号学习兴趣;灵活运用符号解决问题,充分彰显符号多元价值．     

“一”号的三重含义

学习了有理数,算术数的前面就带了正、负号,这种符号在不同场合有着不同的含义和作用,同学们往往分辨不清楚,现将这个“-”号的含义分析如下:一种含义是“负”,表示一个有理数所带的是负号,称为性质符号,如-2,-5等。一种含义是“减”,是表示运算的符号,称为减号。还有一种含义是“相反”,是表示某数的相反数的符号,如在+5的前面加一个“-”号,即-(+5)=-5,就成为它的相反数-5,如果数a<0,那么-a就是它的相反数,即-a>0.对于这个“-”号,在什么时候表示性质符号,读作“负”,什么时候表示运算符号,读作“减”,什么时候表示“相反”,读作某数的相…     

添括号法则的延伸

我们在整式的加减法中已学过了添括号法则：“添括号后,括号前面是‘ ’号,括到括号里的各项都不变符号;添括号后,括号前面是‘-’号,括到括号里的各项都改变符号”．这里的“ ”、“-”号以及括号里的各项之间的连接符号均可看作运算符号．     

去括号 四注意

进行整式加减运算时,首先要去掉括号．去括号是整式加减运算的基础．如何正确去掉括号呢？请同学们注意以下几点：一、要注意括号前面的符号,会运用去括号法则：若括号前是“+”号,去括号后括号内各项都不变号;若括号前是“－”号,去掉括号后括号内各项都要改变符号．要防止出现只改变括号内第一项而忘记改变其余各项符号的错误．例1去括号：（1）sa＋（－6c－3b）;（2）2a－（3b＋Zc）．分析因为（1）式中括号前的符号是“＋”号,所以去括号后括号内的各项都不变号;（2）式中括号前是“－”号,所以去括号后括号内各项都要变号．…     

数学教学中如何挖掘数学符号的暗示功能

“数学的世界是符号化的世界”,“符号是意愿的标志,传播一定的意义,因此,符号能暗示信息”.一般地说,数学符号大致有数字符号、字母符号、运算符号、性质符号、关系符号和图形符号等.数学符号创设的基本原则主要有确定性愿则、简明性原则、方便性原则、启发性原则及和谐性原则     

批改作业“三化”

批改作业是教师检查学生学习情况,取得反馈信息的手段,也是促使学生自我纠正提高的手段。为提高批改质量,教师应实行“三化”。一、符号化改数学作业不宜只打对或错的符号,更不宜代替学生写上正确的式子或结果。教师可与学生约定一些符号,如正确用“√”号,错误用“×”号,理解题意错误用“(?) ?”号,计算错误用“(?)!”号,创造性解法用“☆”号,此处有遗漏用“……”号等等。让学生从这些     

符号“-”的三种作用

在初中数学教学中,有的老师往往只给学生强调“-”号的两种作用:一是作为运算符号,表示“减法运算”,如5-2=3;二是作为用数字表示的实数的性质符号,表示“负”,如-3。以致许多学生错误地理解“-a”前面的“-”号的意义,误认这里的“-”号也是性质符号。其实“-”号还有第三种作用,它表示“将后面字母所表示的数转变为和它自身相反的数,”例如-a是a的相反数。字母a可以表示任何一个实数,当a     

认识“-”号的几种功能

学习有理数后,原来接触的“-”号增加了很多功能,其中有些功能打破了同学们现已形成的思维定势,令同学们很不适应.下面就“-”号的几种功能作一些分析. 一、性质符号课本上有这样一句话:“像-3,-2,-0.5,-151/2等在正数前面加上     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.     

团图为数的图中的闭团贯数

Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.