初中數(shù)學(xué)人教八年級(jí)上冊(cè)第十三章軸對(duì)稱用坐標(biāo)表示軸對(duì)稱 市賽獲獎(jiǎng)PPT

如圖，在平面直角坐標(biāo)系中你能畫出點(diǎn)A關(guān)于x軸的對(duì)稱點(diǎn)嗎?·31425-2-4-1-3012345-4-3-2-1A(2,3)·A’(2,-3)你能說出點(diǎn)A與點(diǎn)A’坐標(biāo)的關(guān)系嗎？x

y探究1關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)是:橫坐標(biāo)不變,縱坐標(biāo)互為相反數(shù).練習(xí):1、點(diǎn)P(-5,6)與點(diǎn)Q關(guān)于x軸對(duì)稱，則點(diǎn)Q的坐標(biāo)為__________.2、點(diǎn)M(a,-5)與點(diǎn)N(-2,b)關(guān)于x軸對(duì)稱，則a=_____,b=_____.(-5,-6)-25歸納如圖，你能在平面直角坐標(biāo)系中畫出點(diǎn)A關(guān)于y軸的對(duì)稱點(diǎn)A’嗎?·31425-2-4-1-3012345-4-3-2-1A(2,3)·A’(-2,3)你能說出點(diǎn)A與點(diǎn)A’坐標(biāo)的關(guān)系嗎？x

y探究2：關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)是:橫坐標(biāo)互為相反數(shù),縱坐標(biāo)不變.練習(xí):1、點(diǎn)P(-5,6)與點(diǎn)Q關(guān)于y軸對(duì)稱，則點(diǎn)Q的坐標(biāo)為__________.2、點(diǎn)M(a,-5)與點(diǎn)N(-2,b)關(guān)于y軸對(duì)稱，則a=_____,b=_____.(5,6)2-5歸納在平面直角坐標(biāo)系中，關(guān)于x軸對(duì)稱的點(diǎn)的橫坐標(biāo)

，縱坐標(biāo)

；關(guān)于y軸對(duì)稱的點(diǎn)橫坐標(biāo)

，縱坐標(biāo)

.即點(diǎn)（x,y)關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)為（，），點(diǎn)（x,y)關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)為（，）.關(guān)于誰對(duì)稱，誰不變，要變就變相反數(shù)。不變互為相反數(shù)互為相反數(shù)不變x-y-x

y歸納小結(jié)1、完成下表.已知點(diǎn)(2,-3)(-1,2)(-6,-5)(0,-1.6)(4,0)關(guān)于x軸的對(duì)稱點(diǎn)關(guān)于y軸的對(duì)稱點(diǎn)(-2,-3)(2,3)(-1,-2)(1,2)(6,-5)(-6,5)(0,-1.6)(0,1.6)(-4,0)(4,0)2、已知點(diǎn)P(2a+b,-3a)與點(diǎn)P’(8,b+2).若點(diǎn)p與點(diǎn)p’關(guān)于x軸對(duì)稱，則a=_____b=_______.若點(diǎn)p與點(diǎn)p’關(guān)于y軸對(duì)稱，則a=_____b=_______.練習(xí)246-203.點(diǎn)P（a-1,-b+2)關(guān)于x軸對(duì)稱的點(diǎn)與關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)相同，則a=_____,b=_____.4.已知點(diǎn)A(-1，-2)和B(1,3),將點(diǎn)A向____平移_____個(gè)單位長(zhǎng)度后得到的點(diǎn)與點(diǎn)B關(guān)于y軸對(duì)稱.5.如圖，四邊形ABCD的四個(gè)頂點(diǎn)的坐標(biāo)分別為A(-5,1),B(-2,1),C(-2,5),D(-5,4),分別畫出與四邊形ABCD關(guān)于y軸和x軸對(duì)稱的圖形.xyABCDA′B′C′D′A′B′C′D′O能力提升：如圖,分別作出點(diǎn)P,M,N關(guān)于直線x=1的對(duì)稱點(diǎn),你能發(fā)現(xiàn)它們坐標(biāo)之間分別有什么關(guān)系嗎?31425-2-4-1-3012345-4-3-2-1···P(-2,3)P′(4,3)M(-1，1)M′(3,1)N(-3,-2)N′(5,-2)x=1x

y

1.坐標(biāo)平面上有一個(gè)軸對(duì)稱圖形，對(duì)稱軸為y=﹣4，此圖形上有一點(diǎn)C(﹣2，﹣9），則點(diǎn)C的對(duì)稱點(diǎn)的坐標(biāo)為_____.2.平面內(nèi)點(diǎn)A（﹣1,2）和點(diǎn)B(﹣1,6）的對(duì)稱軸是_____.課堂小結(jié)用坐標(biāo)表示軸對(duì)稱關(guān)于坐標(biāo)軸對(duì)稱的