14.2.2 用坐標(biāo)表示軸對(duì)稱 ppt課件

1、12.2.2 用坐標(biāo)表示軸對(duì)稱用坐標(biāo)表示軸對(duì)稱軸對(duì)稱圖形軸對(duì)稱圖形探求1：如圖，在平面直角坐標(biāo)系中他能畫出點(diǎn)A關(guān)于x軸的對(duì)稱點(diǎn)嗎?xy31425-2-4-1-3012345-4-3-2-1A (2,3)A(2,-3)探求2：如圖，他能在平面直角坐標(biāo)系中畫出點(diǎn)A關(guān)于y軸的對(duì)稱點(diǎn)嗎?31425-2-4-1-3012345-4-3-2-1A (2,3)A(-2,3)A(2,-3)小結(jié)：在平面直角坐標(biāo)系中，關(guān)于x軸對(duì)稱的點(diǎn)關(guān)于y軸對(duì)稱的點(diǎn)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_.(x, y)( x, y)橫坐標(biāo)不變橫坐標(biāo)不變,縱坐標(biāo)互為相反數(shù)縱坐標(biāo)互為相反數(shù).縱坐標(biāo)不變縱坐標(biāo)不變,

2、橫坐標(biāo)互為相反數(shù)橫坐標(biāo)互為相反數(shù).點(diǎn)點(diǎn)x, y關(guān)于關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)為軸對(duì)稱的點(diǎn)的坐標(biāo)為_.提高題、知點(diǎn)提高題、知點(diǎn)P(2 , b)與點(diǎn)與點(diǎn)P(a , -8).假設(shè)點(diǎn)假設(shè)點(diǎn)p與點(diǎn)與點(diǎn)p關(guān)于關(guān)于x軸對(duì)稱，那么軸對(duì)稱，那么a=_ b=_.假設(shè)點(diǎn)假設(shè)點(diǎn)p與點(diǎn)與點(diǎn)p關(guān)于關(guān)于y軸對(duì)稱，那么軸對(duì)稱，那么a=_ b=_.練 習(xí)28-2-8例：如圖1，根據(jù)要求回答以下問題：1點(diǎn)A關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)是A點(diǎn)B關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)是B點(diǎn)C關(guān)于軸對(duì)稱的點(diǎn)的坐標(biāo)是CA31425-2-4-1-301 2 3 4 5-4 -3 -2 -1CBBACAC(2作出與ABC關(guān)于x軸對(duì)稱的圖形BB這節(jié)課他學(xué)到了什么？1 1、他能寫出平面坐標(biāo)系中一個(gè)點(diǎn)關(guān)于、他能寫出平面坐標(biāo)系中一個(gè)點(diǎn)關(guān)于x x軸和軸和y y軸軸對(duì)稱的點(diǎn)的坐標(biāo)嗎？對(duì)稱的點(diǎn)的坐標(biāo)嗎？關(guān)于關(guān)于x軸對(duì)稱的點(diǎn)橫坐標(biāo)相等軸對(duì)稱的點(diǎn)橫坐標(biāo)相等,縱坐標(biāo)互為相反數(shù)縱坐標(biāo)互為相反數(shù).關(guān)于關(guān)于y軸軸對(duì)稱的點(diǎn)橫坐標(biāo)互為相反數(shù)對(duì)稱的點(diǎn)橫坐標(biāo)互為相反數(shù),縱坐標(biāo)相等縱坐標(biāo)相等.2、他能在平面直角坐標(biāo)系中畫出一個(gè)圖形關(guān)于、他能在平面直角坐標(biāo)系中畫出一個(gè)圖形關(guān)于x軸或軸或y軸的對(duì)稱圖形嗎？軸的對(duì)稱圖形嗎？先求出知圖形中的一些特殊點(diǎn)先求出知圖形中的一些特殊點(diǎn)(如多邊形的頂點(diǎn)如多邊形的頂點(diǎn))的對(duì)應(yīng)點(diǎn)的坐的對(duì)應(yīng)點(diǎn)的坐標(biāo)標(biāo),描出并