( 1 )作△ABC關(guān)于y軸的對(duì)稱(chēng)圖形△A1B1C1 , 寫(xiě)出點(diǎn)C關(guān)于y軸的對(duì)稱(chēng)點(diǎn)C1的坐標(biāo);
( 2 )作△ABC關(guān)于直線(xiàn)m(直線(xiàn)m上各點(diǎn)的縱坐標(biāo)都為-1)的對(duì)稱(chēng)圖形△A2B2C2 , 寫(xiě)出點(diǎn)C關(guān)于直線(xiàn)m的對(duì)稱(chēng)點(diǎn)C2的坐標(biāo).
① 與 軸的位置關(guān)系怎樣?說(shuō)明理由;
②求 的長(zhǎng).