1、關(guān)于原點(diǎn)對(duì)稱的點(diǎn)的坐標(biāo),在平面直角坐標(biāo)系中畫出下列各點(diǎn)關(guān)于x軸的對(duì)稱點(diǎn).,B (-4, 2),C(3, -4),B (-4, -2),C(3, 4),思考：關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)具有怎樣的關(guān)系？,在平面直角坐標(biāo)系中畫出下列各點(diǎn)關(guān)于y軸的對(duì)稱點(diǎn).,B (-4, 2),C(3, -4),B (4, 2),C(-3, -4),小結(jié)：在平面直角坐標(biāo)系中，關(guān)于x軸對(duì)稱的點(diǎn)橫坐標(biāo)相等,縱坐標(biāo)互為相反數(shù).關(guān)于y軸對(duì)稱的點(diǎn)橫坐標(biāo)互為相反數(shù),縱坐標(biāo)相等.,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_.,(x,y),(x,y),在平面直角坐標(biāo)系中畫出下列各點(diǎn)關(guān)于原點(diǎn)的對(duì)稱點(diǎn)

2、.,C (-3, 4),C(3, -4),B (4, 2),B(-4,-2),小結(jié)：在平面直角坐標(biāo)系中，關(guān)于原點(diǎn)對(duì)稱的點(diǎn) 橫坐標(biāo)互為相反數(shù), 縱坐標(biāo)互為相反數(shù).,點(diǎn)（x, y）關(guān)于x軸對(duì)稱 的點(diǎn)的坐標(biāo)為_.,(-x,y),1、完成下表.,(-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=_. 若點(diǎn)p與點(diǎn)p關(guān)于原點(diǎn)對(duì)稱，則a=_ b=_.,練 習(xí),4,6,

3、-20,2,3.下列圖象中,一定關(guān)于原點(diǎn)對(duì)稱的圖象是( ) A.y=1/x B.y=2x+1 C.y=-2x+1 D.以上三種都有可能.,例：已知ABC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ABC關(guān)于原點(diǎn)對(duì)稱的圖形。,解：點(diǎn)A(-3,5),B(-4,1), C(-1,3)，關(guān)于y軸對(duì)稱 點(diǎn)的坐標(biāo)分別為A(3,5), B(4,1),C(1,3).依次連接AB,BC,CA,就得到ABC關(guān)于y軸對(duì)稱的ABC.,-5,A,B,C,1.四邊形ABCD各頂點(diǎn)坐標(biāo)分別為(5,0),(-2,3)，（-1,0) ,(-1,5),作出與四邊形ABCD關(guān)于原點(diǎn)O對(duì)稱的圖形.,2.平行四邊形,A(1,2), B(-4,2), C(-2,-5),求出第四個(gè)點(diǎn)D的坐標(biāo).,若平行四邊形在坐標(biāo)系內(nèi)關(guān)于原點(diǎn)對(duì)稱,已知點(diǎn)A,點(diǎn)B的坐標(biāo)不變,點(diǎn)C,點(diǎn)D的坐標(biāo)又是什么?,1、學(xué)習(xí)了在平面直角坐標(biāo)系中，關(guān)于x軸和y軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)。,關(guān)于x軸對(duì)稱的點(diǎn)橫坐標(biāo)相等,縱坐標(biāo)互為相反數(shù).關(guān)于y軸對(duì)