13.2.1作軸對(duì)稱圖形 課件2024-2025學(xué)年人教版 數(shù)學(xué)八年級(jí)上冊(cè)

13.2畫軸對(duì)稱圖形第1課時(shí)

作軸對(duì)稱圖形學(xué)習(xí)目標(biāo)1.通過(guò)實(shí)際操作掌握做軸對(duì)稱圖形的方法2.經(jīng)歷畫一般的軸對(duì)稱圖形的過(guò)程，能夠按要求做出簡(jiǎn)單平面圖形，經(jīng)過(guò)一次對(duì)稱后的圖形復(fù)習(xí)：軸對(duì)稱圖形和兩個(gè)圖形成軸對(duì)稱1.如果一個(gè)平面圖形沿一條直線折疊，直線兩旁的部分能夠互相重合，這個(gè)圖形就叫做軸對(duì)稱圖形，這條直線即折痕所在的直線就是它的對(duì)稱軸2.把一個(gè)圖形沿著某一條直線折疊，如果它能夠與另一個(gè)圖形重合，那么就說(shuō)這兩個(gè)圖形關(guān)于這條直線對(duì)稱或者說(shuō)這兩個(gè)圖形形成軸對(duì)稱，這條直線叫做對(duì)稱軸復(fù)習(xí)：軸對(duì)稱的性質(zhì)成軸對(duì)稱的兩個(gè)圖形全等，即對(duì)應(yīng)線段相等，對(duì)應(yīng)角相等PAC=A′C′BC=B′C′AB=A′B′∠A=∠A′∠B=∠B′∠C=∠C′mQ復(fù)習(xí)：對(duì)稱點(diǎn)折疊后重合的點(diǎn)是對(duì)應(yīng)點(diǎn)，叫做對(duì)稱點(diǎn)新圖形上的每一點(diǎn)都是原圖形上的某一點(diǎn)，關(guān)于直線m的對(duì)稱點(diǎn)PmQ復(fù)習(xí)：對(duì)應(yīng)點(diǎn)所連線段與對(duì)稱軸的關(guān)系如果兩個(gè)圖形關(guān)于某條直線對(duì)稱，對(duì)稱軸是任何一對(duì)對(duì)稱點(diǎn)所連線段的垂直平分線mmAA′B′B軸對(duì)稱圖形的對(duì)稱軸，是任何一對(duì)對(duì)稱點(diǎn)所連線段的垂直平分線作軸對(duì)稱圖形如圖，已知點(diǎn)A和直線l，試畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′.作軸對(duì)稱圖形（1）過(guò)點(diǎn)a作對(duì)稱軸l的垂線，垂足為o；如圖，已知點(diǎn)A和直線l，試畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′.作軸對(duì)稱圖形（1）過(guò)點(diǎn)a作對(duì)稱軸l的垂線，垂足為o；（2）在垂線上截取ao'=ao.點(diǎn)a'就是點(diǎn)a關(guān)于直線l的對(duì)稱點(diǎn)如圖，已知點(diǎn)A和直線l，試畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′.作軸對(duì)稱圖形如圖，已知線段AB和直線l，試畫出線段AB關(guān)于直線l的對(duì)稱線段.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；作軸對(duì)稱圖形如圖，已知線段AB和直線l，試畫出線段AB關(guān)于直線l的對(duì)稱線段.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；作軸對(duì)稱圖形如圖，已知線段AB和直線l，試畫出線段AB關(guān)于直線l的對(duì)稱線段.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；作軸對(duì)稱圖形如圖，已知線段AB和直線l，試畫出線段AB關(guān)于直線l的對(duì)稱線段.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；（2）畫出點(diǎn)B關(guān)于直線l的對(duì)稱點(diǎn)B′；作軸對(duì)稱圖形如圖，已知線段AB和直線l，試畫出線段AB關(guān)于直線l的對(duì)稱線段.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；（2）畫出點(diǎn)B關(guān)于直線l的對(duì)稱點(diǎn)B′；（3）連接點(diǎn)A′和點(diǎn)B′成線段A′B′，線段A′B′即為所求。作軸對(duì)稱圖形如圖，已知△ABC和直線l，試畫出△ABC關(guān)于直線l的對(duì)稱圖形.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；作軸對(duì)稱圖形如圖，已知△ABC和直線l，試畫出△ABC關(guān)于直線l的對(duì)稱圖形.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；作軸對(duì)稱圖形如圖，已知△ABC和直線l，試畫出△ABC關(guān)于直線l的對(duì)稱圖形.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；（2）畫出點(diǎn)B和點(diǎn)C關(guān)于直線l的對(duì)稱點(diǎn)B′和C′；作軸對(duì)稱圖形如圖，已知△ABC和直線l，試畫出△ABC關(guān)于直線l的對(duì)稱圖形.（1）畫出點(diǎn)A關(guān)于直線l的對(duì)稱點(diǎn)A′；（2）畫出點(diǎn)B和點(diǎn)C關(guān)于直線l的對(duì)稱點(diǎn)B′和C′；（3）連接A′B′，B′C′，C′A′，則△A′B′C′即為所求.小結(jié)作已知圖形關(guān)于已知直線對(duì)稱的圖形的一般步驟：1、找點(diǎn)（確定圖形中的一些特殊點(diǎn)）2、畫點(diǎn)（畫出特殊點(diǎn)關(guān)于已知直線的對(duì)稱點(diǎn)）3、連線【例題】如圖所示，D