【正文】
C,PD=30 , 則AM= 軸對(duì)稱變換由一個(gè)平面圖形得到它的軸對(duì)稱圖形叫做軸對(duì)稱變換.成軸對(duì)稱的兩個(gè)圖形中的任何一個(gè)可以看著由另一個(gè)圖形經(jīng)過(guò)軸對(duì)稱變換后得到.軸對(duì)稱變換的性質(zhì)(1)經(jīng)過(guò)軸對(duì)稱變換得到的圖形與原圖形的形狀、大小完全一樣(2)經(jīng)過(guò)軸對(duì)稱變換得到的圖形上的每一點(diǎn)都是原圖形上的某一點(diǎn)關(guān)于對(duì)稱軸的對(duì)稱點(diǎn).(3)連接任意一對(duì)對(duì)應(yīng)點(diǎn)的線段被對(duì)稱軸垂直平分.作一個(gè)圖形關(guān)于某條直線的軸對(duì)稱圖形(1)作出一些關(guān)鍵點(diǎn)或特殊點(diǎn)的對(duì)稱點(diǎn).(2)按原圖形的連接方式連接所得到的對(duì)稱點(diǎn),即得到原圖形的軸對(duì)稱圖形.關(guān)于坐標(biāo)軸對(duì)稱點(diǎn)P(x,y)關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)是(x,-y)點(diǎn)P(x,y)關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)是(-x,y)關(guān)于原點(diǎn)對(duì)稱點(diǎn)P(x,y)關(guān)于原點(diǎn)對(duì)稱的點(diǎn)的坐標(biāo)是(-x,-y)關(guān)于坐標(biāo)軸夾角平分線對(duì)稱點(diǎn)P(x,y)關(guān)于第一、三象限坐標(biāo)軸夾角平分線y=x對(duì)稱的點(diǎn)的坐標(biāo)是(y,x)點(diǎn)P(x,y)關(guān)于第二、四象限坐標(biāo)軸夾角平分線y= -x對(duì)稱的點(diǎn)的坐標(biāo)是(-y,-x)關(guān)于平行于坐標(biāo)軸的直線對(duì)稱點(diǎn)P(x,y)關(guān)于直線x=m對(duì)稱的點(diǎn)的坐標(biāo)是(2m-x,y);點(diǎn)P(x,y)關(guān)于直線y=n對(duì)稱的點(diǎn)的坐標(biāo)是(x,2n-y);考點(diǎn)二、軸對(duì)稱變換及用坐標(biāo)表示軸對(duì)稱1. 點(diǎn) A(3 ,2)關(guān)于 y 軸對(duì)稱點(diǎn)的坐標(biāo)是( ) A (3 ,2) B (3 ,2) C (3 ,2) D?。? ,3) 2.點(diǎn)P(a,b)關(guān)于 x 軸的對(duì)稱點(diǎn)為P'(1,6),則A、B的值分別為( ) A 1 ,6 B 1 ,6 C 1 ,6 D 1 ,6 軸對(duì)稱點(diǎn)P'的坐標(biāo)為(4,5),那么點(diǎn)P關(guān)于y軸對(duì)稱點(diǎn)P的坐標(biāo)為: A(4,5) B (4,5) C (4,5) D (5,4) (1,2)和點(diǎn)B(1,6)的對(duì)稱軸是( ) =4 =1 直線 x=1 對(duì)稱的點(diǎn)是( ) A 點(diǎn)(0 ,3)與點(diǎn)(2 ,3) B 點(diǎn)(2 ,3)與點(diǎn)(2 ,3)C 點(diǎn)(2 ,3)與點(diǎn)(0 ,3)