學(xué)設(shè)第十三章軸對(duì)稱13.2畫軸對(duì)稱圖形13.2

畫軸對(duì)稱圖形(時(shí)學(xué)習(xí)目標(biāo)1在平面直角坐標(biāo)系會(huì)畫出關(guān)于x軸軸稱的,而探求關(guān)于軸對(duì)稱點(diǎn)的坐標(biāo)規(guī)律2通過找關(guān)于坐標(biāo)軸對(duì)稱的點(diǎn)之間的規(guī)律以在驗(yàn)證規(guī)律正確的過程中培語言能力、觀察能力、歸納能力養(yǎng)良好的科學(xué)研究方法3在找點(diǎn)與繪圖的過程,展數(shù)形結(jié)合的思維意識(shí)形數(shù)形結(jié)合的思想學(xué)習(xí)過程一、自主學(xué)習(xí)已知對(duì)稱軸l

和一個(gè)點(diǎn)A你能作出點(diǎn)A關(guān)于

的對(duì)稱點(diǎn)嗎?思:是一幅老北京城的示意圖中西直門和東直門是關(guān)于中軸線對(duì)稱的.如果以天安門為原點(diǎn)分別以長安街和中軸線為和軸立平面直角坐標(biāo)系根如圖所示的東直門的坐標(biāo)你說出西直門的坐標(biāo)嗎/6

學(xué)設(shè)二、深化探究探究如圖在面直角坐標(biāo)中你能畫出點(diǎn)(2,3)關(guān)于的對(duì)稱點(diǎn)?點(diǎn)B4,2),-4),,1呢?歸納:關(guān)于x軸稱的點(diǎn)的坐標(biāo)的特點(diǎn)練習(xí):

.1點(diǎn)P5,6)與關(guān)軸稱則Q的標(biāo)為2點(diǎn)(a-5)點(diǎn)(2,)關(guān)于x軸稱則

.,.探究如圖你在平面直角標(biāo)系中畫出點(diǎn)(2,3)關(guān)于的對(duì)稱點(diǎn)?點(diǎn)B4,2),-4)呢?歸納:關(guān)于y軸稱的點(diǎn)的坐標(biāo)的特點(diǎn)練習(xí):

.1點(diǎn)P5,6)與關(guān)軸稱則Q的標(biāo)為2點(diǎn)(a-5)點(diǎn)(2,)關(guān)于y軸稱則

.,.小結(jié):點(diǎn),y)關(guān)軸對(duì)稱的點(diǎn)的坐標(biāo)為

.點(diǎn),y)關(guān)于y軸稱的點(diǎn)的坐標(biāo)為三、深化提高1完成下表

.已知點(diǎn)A(3,

-

(

-1,2)

(8,

-

(0,

-

(4,0)關(guān)于x軸的/6

學(xué)設(shè)對(duì)稱點(diǎn)關(guān)于y軸的對(duì)稱點(diǎn)2已知點(diǎn)P(2a+b3)點(diǎn)b+2).若點(diǎn)與關(guān)于軸對(duì)則a=若點(diǎn)與關(guān)于軸對(duì)則a=

,,3【例】已eq\o\ac(△,)的個(gè)頂點(diǎn)的坐標(biāo)分別((--1,3),作eq\o\ac(△,)ABC關(guān)于y軸稱的圖.【例2】四邊形的個(gè)頂點(diǎn)的坐標(biāo)分別為(-5,1),B-2,1),-2,5),(5,4),分作出四邊形關(guān)于y軸x軸稱的圖解點(diǎn)xy關(guān)軸對(duì)稱的點(diǎn)的坐標(biāo)為-xy因四邊形ABCD的頂點(diǎn)AB,關(guān)軸稱點(diǎn)分別為A',),(,C'

,D',

依連接A'B'B'C',D'A'就得到與四邊形關(guān)于y軸稱的四邊形類似地,你在圖上作出與四邊形關(guān)于對(duì)稱的圖形四、總結(jié)反思/6

學(xué)設(shè)這節(jié)課你學(xué)到了什么五、課堂檢測1分別寫出下列各點(diǎn)關(guān)于x軸軸對(duì)稱的點(diǎn)的坐標(biāo)(

-2,6)(1,

-(

-1,3)(

-

-(1,0)2

關(guān)于x軸對(duì)稱的點(diǎn)關(guān)于y軸對(duì)稱的點(diǎn)若點(diǎn)(2,于軸的對(duì)稱點(diǎn)為A關(guān)軸的對(duì)稱點(diǎn)為B的積為

.3已知點(diǎn)P(2m+m-3)關(guān)于y軸對(duì)稱點(diǎn)在第四象,求m的值.4

如,利關(guān)于坐標(biāo)軸對(duì)稱點(diǎn)的坐標(biāo)特點(diǎn),分作出與關(guān)x軸稱的A'B'C'和關(guān)于軸對(duì)稱eq\o\ac(△,)″B參考答案一、自主學(xué)習(xí)過點(diǎn)作線

的垂線段AO⊥,垂足為O延到使(),則A'是點(diǎn)關(guān)于直線l二、深化探究探究1:

的對(duì)稱點(diǎn)./6

學(xué)設(shè)橫坐標(biāo)不變縱坐標(biāo)互為相反數(shù)練習(xí):1(6)2.-25探究2:縱坐標(biāo)不變橫坐標(biāo)互為相反數(shù)練習(xí):1(5,6)22三、深化提高1

-5已知點(diǎn)

(3,-3)B(1,2)C(8,5)(0,-1)(4,0)關(guān)于x軸的對(duì)稱點(diǎn)

(3,3)(

-

-(8,5)(0,1)(4,0)關(guān)于y軸的對(duì)稱點(diǎn)

(

-

-(1,2)(

-

-(0,

-(

-4,0)2246

203【例1如所示【例】如所./6

學(xué)設(shè)五、課堂檢測1(

-2,6)(1,

-

(

-1,3)(

4,

-

(1,0)關(guān)于x軸對(duì)稱的點(diǎn)

(

-

-

(1,2)

(

-

-(

-4,2)

(1,0)關(guān)于y軸對(duì)稱的點(diǎn)

(2,6)

(

-