1422用坐標(biāo)表示軸對(duì)稱--

1、動(dòng)動(dòng)手動(dòng)動(dòng)手畫一畫畫一畫 你能畫出你能畫出點(diǎn)點(diǎn)a關(guān)于已關(guān)于已知直知直mn的對(duì)稱點(diǎn)嗎的對(duì)稱點(diǎn)嗎?aamno探究探究1：如圖，在平面直角坐標(biāo)系中你：如圖，在平面直角坐標(biāo)系中你能畫出點(diǎn)能畫出點(diǎn)a關(guān)于關(guān)于x軸的對(duì)稱點(diǎn)嗎軸的對(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？在平面直角坐標(biāo)系中畫出下列各點(diǎn)在平面直角坐標(biāo)系中畫出下列各點(diǎn)關(guān)于關(guān)于x軸的對(duì)稱點(diǎn)軸的對(duì)稱點(diǎn).31425-2-4-1-301 2 3 4 5-4 -3 -2 -1b (-4, 2)c(3, -4)b (-4, -2)c(3, 4)思考：思考：關(guān)于關(guān)于x軸軸對(duì)稱的對(duì)

2、稱的點(diǎn)的坐點(diǎn)的坐標(biāo)具有標(biāo)具有怎樣的怎樣的關(guān)系？關(guān)系？歸納：關(guān)于歸納：關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)的特軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)是點(diǎn)是:橫坐標(biāo)橫坐標(biāo)相等相等,縱坐標(biāo)互為縱坐標(biāo)互為相反數(shù)相反數(shù).練習(xí)練習(xí):1、點(diǎn)、點(diǎn)p(-5, 6)與點(diǎn)與點(diǎn)q關(guān)于關(guān)于x軸對(duì)稱，則點(diǎn)軸對(duì)稱，則點(diǎn)q的坐標(biāo)為的坐標(biāo)為_.2、點(diǎn)、點(diǎn)m(a, -5)與點(diǎn)與點(diǎn)n(-2, b)關(guān)于關(guān)于x軸對(duì)稱，軸對(duì)稱，則則a=_, b =_.(- 5 , -6 )-25探究探究2：如圖，你能在平面直角坐標(biāo)系：如圖，你能在平面直角坐標(biāo)系中畫出點(diǎn)中畫出點(diǎn)a關(guān)于關(guān)于y軸的對(duì)稱點(diǎn)嗎軸的對(duì)稱點(diǎn)嗎?31425-2-4-1-3012345-4-3-2-1a (2,3)a

3、(-2,3)你能說出點(diǎn)a與點(diǎn)a坐標(biāo)的關(guān)系嗎？在平面直角坐標(biāo)系中畫出下列各點(diǎn)在平面直角坐標(biāo)系中畫出下列各點(diǎn)關(guān)于關(guān)于y軸的對(duì)稱點(diǎn)軸的對(duì)稱點(diǎn).31425-2-4-1-301 2 3 4 5-4 -3 -2 -1b (-4, 2)c(3, -4)b (4, 2)c(-3, -4)思考：思考：關(guān)于關(guān)于y軸軸對(duì)稱的對(duì)稱的點(diǎn)的坐點(diǎn)的坐標(biāo)具有標(biāo)具有怎樣的怎樣的關(guān)系？關(guān)系？歸納：關(guān)于歸納：關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)的特軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)是點(diǎn)是:橫坐標(biāo)互為橫坐標(biāo)互為相反數(shù)相反數(shù),縱坐標(biāo)縱坐標(biāo)相等相等.練習(xí)練習(xí):1、點(diǎn)、點(diǎn)p(-5, 6)與點(diǎn)與點(diǎn)q關(guān)于關(guān)于y軸對(duì)稱，則軸對(duì)稱，則點(diǎn)點(diǎn)q的坐標(biāo)為的坐標(biāo)為_.2、點(diǎn)、點(diǎn)m

4、(a, -5)與點(diǎn)與點(diǎn)n(-2, b)關(guān)于關(guān)于y軸對(duì)軸對(duì)稱，則稱，則a=_, b =_.( 5 , 6 )2-5小結(jié)：小結(jié)：在平面直角坐標(biāo)系中，關(guān)于在平面直角坐標(biāo)系中，關(guān)于x軸對(duì)稱的點(diǎn)軸對(duì)稱的點(diǎn)橫坐標(biāo)相等橫坐標(biāo)相等,縱坐標(biāo)互為相縱坐標(biāo)互為相反數(shù)反數(shù).關(guān)于關(guān)于y軸對(duì)稱的點(diǎn)軸對(duì)稱的點(diǎn)橫坐標(biāo)互為相反橫坐標(biāo)互為相反數(shù)數(shù),縱坐標(biāo)相等縱坐標(biāo)相等.點(diǎn)（點(diǎn)（x, y）關(guān)于關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)為軸對(duì)稱的點(diǎn)的坐標(biāo)為_.點(diǎn)（點(diǎn)（x, y）關(guān)于關(guān)于y軸對(duì)稱的點(diǎn)軸對(duì)稱的點(diǎn)的坐標(biāo)為的坐標(biāo)為_.(x, y)( x, y)1、完成下表、完成下表.已知點(diǎn)已知點(diǎn)(2,-3) (-1,2) (-6,-5) (0,-1.6) (4

5、,0)關(guān)于關(guān)于x軸的對(duì)稱點(diǎn)軸的對(duì)稱點(diǎn)關(guān)于關(guān)于y軸的對(duì)稱點(diǎn)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)、已知點(diǎn)p(2a+b,-3a)與點(diǎn)與點(diǎn)p(8,b+2).若點(diǎn)若點(diǎn)p與點(diǎn)與點(diǎn)p關(guān)于關(guān)于x軸對(duì)稱，則軸對(duì)稱，則a=_ b=_.若點(diǎn)若點(diǎn)p與點(diǎn)與點(diǎn)p關(guān)于關(guān)于y軸對(duì)稱，則軸對(duì)稱，則a=_ b=_.練練 習(xí)習(xí):246-20例：已知例：已知abc的三個(gè)頂點(diǎn)的坐標(biāo)分別為的三個(gè)頂點(diǎn)的坐標(biāo)分別為a(-3，5),b(- 4，1),c(-1，3)，作出，作出abc關(guān)于關(guān)于y軸對(duì)稱的圖形。軸對(duì)稱的圖形。a31

6、425-2-4-1-3012345-4 -3 -2 -1cbbac探究探究3:如圖如圖,分別作出點(diǎn)分別作出點(diǎn)p,m,n關(guān)于直線關(guān)于直線x=1的對(duì)稱點(diǎn)的對(duì)稱點(diǎn), 你能發(fā)現(xiàn)它們坐標(biāo)之間分你能發(fā)現(xiàn)它們坐標(biāo)之間分別有什么關(guān)系嗎別有什么關(guān)系嗎?31425-2-4-1-3012345-4-3-2-1x=1p(-2,3)m(-1,1)n(5,-2)n(-3,-2)m(3,1)p(4,3)思考:1、在平面直角坐標(biāo)系中,點(diǎn)(x,y)關(guān)于直線x=1對(duì)稱點(diǎn)的坐標(biāo)是多少? 2 2、在平面直角坐標(biāo)系中、在平面直角坐標(biāo)系中, ,點(diǎn)點(diǎn)(x, y)(x, y)關(guān)于直線關(guān)于直線x=-1x=-1對(duì)稱對(duì)稱點(diǎn)的坐標(biāo)是多少點(diǎn)的坐標(biāo)是多少? ? 3 3、在平面直角坐標(biāo)系、在平面直角坐標(biāo)系中中, ,點(diǎn)點(diǎn)(x,y)(x,y)關(guān)于直線關(guān)于直線y=1y=1對(duì)對(duì)稱點(diǎn)的坐標(biāo)是多