《实数》ppt课件1

实数知识回顾1、无理数：无限不循环小数叫做无理数2、有理数：有限和无限循环小数属于有理数或整数与分数统称为有理数（1）到目前为止，你认识了哪些数？自然数分数负数有理数小数负整数正整数零有限小数无限不循环小数-无理数负有理数实数有理数无理数正有理数负有理数零正无理数负无理数无限不循环小数（2）你会把实数加以分类吗？你所确定的分类标准是什么？按你确定的标准进行一次分类后，还能再确定另一个指标作为标准，把其中的每一类再进一步分类吗？有限小数或无限循环小数按性质分类正有理数正无理数负有理数负无理数实数实数正实数负实数按大小分类有一定的规律，但不循环的无限小数都是无理数。0.1010010001…〔两个1之间依次多1个0〕—234.232232223…〔两个3之间依次多1个2〕0.12345678910111213…〔小数部分有相继的正整数组成〕例如像的数是无理数。12,3,7是有理数2552525圆周率及一些含有的数都是无理数12,2,思考：一个无理数的相反数与绝对值分别是什么数？例1下列各数哪些是有理数？哪些是无理数？哪些是正数？哪些是负数？√-8，√8，π，0.27，0，-5.151151115…（相邻两个5之间一次多1个1），0.101001，22/7，-√3/3，5.15.3...解：有理数：√-8，0.27，0.101001,22/7，5.15；3...无理数：√8，π，-5.151151115…-√3/3；正数：√8，π，0.27，0.101001,22/7，5.15；...负数：√-8，-5.151151115…-√3/3.3练习将下列各数放入图中适当的位置：-0.101001000100001、、4、3.14、27225有理数无理数整数正整数250.373373337……40、-2-0.101001000100001、3.14、7220.373373337…(它的位数无限且相邻的两个3之间7的个数依次加1)0、-2、0.23..0.23、、、..练习判断下列说法是否正确：4）实数可以分为正实数和负实数两类5）无理数包括正无理数、零、负无理数.6）有理数都是有限小数。…（）…（）……………………（）1）无限小数都是无理数；2）无理数都是无限小数；3）正实数包括正有理数和正无理数；……………………（）…………………（）………（）议一议12AB如图:OA=OB,数轴上A点对应的数是什么?如果将所有有理数都标到数轴上,那么数轴被填满了吗?210-11、每个实数都可以用数轴上的一个点来表示;反过来,数轴上的每一个点都表示一个实数.即实数和数轴上点是一一对应的.2、同样,在数轴上,右边的点表示的数比左边的点表示的数大.总结：4、有序实数对与坐标平面上的点也是一一对应的。3、如果a是实数，那么｜a｜就是在数轴上表示数a的点，到原点的距离。在实数范围内，相反数、倒数、绝对值的意义和有理数范围内的相反数、倒数、绝对值的意义完全一样。重要结论重要结论在数轴上作出的对应点.50123-1125012-1-2A一个实数a-1-10-110-1510-13510-13510-153531530153-1015351、每个实数都可以用数轴上的一个点来表示;反过来,数轴上的每一个点都表示一个实数.即实数和数轴上点是一一对应的.2、同样,在数轴上,右边的点表示的数比左边的点表示的数大.数轴上一个点有一个实数点数有一个实数数轴上一个点数点例如：互为相反数，和2-2互为倒数，和51533.|-|,0|0|,3|3|例2比较下列各组数中两个数的大小：（1）3.14与π；（2）-√3与√-3.3解：（1）∵π≈3.141，∴3.14π.（2）∵-√3≈-1.732，√-3≈-1.442∴-√3√-333shop.99114.com/50657958shop.99114.com/50498383shop.99114.com/47774270shop.99114.com/50607661shop.99114.com/50657309shop.99114.com/50662497shop.99114.com/47859702shop.99114.com/50521841shop.99114.com/49151641shop.99114.com/50648237shop.99114.com/50640413shop.99114.com/50532750shop.99114.com/43562073shop.99114.com/50632314shop.99114.com/50299211shop.99114.com/49764738shop.99114.com/50646709shop.99114.com/50608292shop.99114.com/50642730shop.99114.com/50662546shop.99114.com/50663613shop.99114.com/49783030shop.99114.com/50631631shop.99114.com/47773595shop.99114.com/49827561shop.99114.com/50674736shop.99114.com/49766140shop.99114.com/47849249shop.99114.com/50669560shop.99114.com/50658420shop.99114.com/50659587shop.99114.com/50510133shop.99114.com/50629770shop.99114.com/50656890shop.99114.com/41498558shop.99114.com/49824056shop.99114.com/47864808shop.99114.com/45414995shop.99114.com/49687733shop.99114.com/50672978shop.99114.com/50673083shop.99114.com/47878067shop.99114.com/50649987shop.99114.com/50617012shop.99114.com/50665145shop.99114.com/50647123shop.99114.com/50292167shop.99114.com/50655190shop.99114.com/50627787shop.99114.com/50659871shop.99114.com/50513305shop.99114.com/50662881shop.99114.com/50665133shop.99114.com/50653799shop.99114.com/50659034shop.99114.com/50666877shop.99114.com/50654456shop.99114.com/50656905shop.99114.com/50823560shop.99114.com/50658603shop.99114.com/50664977shop.99114.com/50489520shop.99114.com/50294049shop.99114.com/50508111shop.99114.com/50578361shop.99114.com/50661888shop.99114.com/50637656shop.99114.com/50670631shop.99114.com/50497599shop.99114.com/50626129shop.99114.com/50665651shop.99114.com/50662632shop.99114.com/50477386shop.99114.com/42298014shop.99114.com/50523857shop.99114.com/50664627shop.99114.com/50672524shop.99114.com/50667797shop.99114.com/50601952shop.99114.com/50628845shop.99114.com/50639356shop.99114.com/50672506shop.99114.com/50639813shop.99114.com/50587461shop.99114.com/50532719shop.99114.com/50657075shop.99114.com/50659646shop.99114.com/50674761shop.99114.com/50801644shop.99114.com/50648576shop.99114.com/49705090shop.99114.com/50658375shop.99114.com/50658371shop.99114.com/50655033shop.99114.com/50812991shop.99114.com/50665062shop.99114.com/50512368shop.99114.com/50672963shop.99114.com/50578366shop.99114.com/50813319例3求下列各数的相反数和绝对值：（1）2-√3；（2）√5-√6.解：（1）2-√3的相反数是-（2-√3）=-2+√3∵√32，∴2-√30，∴|2-√3|=2-√3.（2）√5-√6的相反数是-（√5-√6）=-√5+√6=√6-√5∵√5√6，∴√5-√60，∴|√5-√6|=√6-√5.练习：求下列各数的相反数、倒数和绝对值：。绝对值是；倒数是；的相反数是7(1)7777.8-)2(3绝对值是；倒数是；的相反数是2212.49)3(绝对值是；倒数是；的相反数是-77171、a、b互为相反数，c与d互为倒数则a+1+b+cd=。2、实数a,b,c,d在数轴上的对应点如图1－1所示，则它们从小到大的顺序是。cd0ba图1－1－1其中：bacdbcda2cdbaa+b-d-cb-ca-d练习：总结与回顾这节课你有什么收获？你对本节课的内容还有哪些疑问？