1、第2章 圖形的軸對(duì)稱2.2軸對(duì)稱的基本性質(zhì)第2課時(shí)學(xué)習(xí)目標(biāo)知道平面直角坐標(biāo)系中，關(guān)于坐標(biāo)軸的對(duì)稱點(diǎn)的關(guān)系。會(huì)用平面直角坐標(biāo)系中，關(guān)于坐標(biāo)軸的對(duì)稱點(diǎn)的關(guān)系，求已知點(diǎn)關(guān)于坐標(biāo)軸的對(duì)稱點(diǎn)。合作交流1.如圖，平面直角坐標(biāo)系中有長(zhǎng)方形ABCD:xyODABC(3, 5)(3, 5)(3, 5)(3, 5)(1)若點(diǎn)A與點(diǎn)B關(guān)于X軸對(duì)稱，B點(diǎn)的坐標(biāo)是什么？點(diǎn)C與點(diǎn)D關(guān)于X軸對(duì)稱,D點(diǎn)坐標(biāo)是什么呢？(2)關(guān)于x軸對(duì)稱的點(diǎn)的坐標(biāo)有什么特征？關(guān)于x軸對(duì)稱的點(diǎn)橫坐標(biāo)相同，縱坐標(biāo)互為相反數(shù)歸納：關(guān)于X軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)是:橫坐標(biāo)相同,縱坐標(biāo)互為相反數(shù).練習(xí):1、點(diǎn)P(-4, 7)與點(diǎn)Q關(guān)于x軸對(duì)稱，則點(diǎn)Q的坐標(biāo)

2、為_.2、點(diǎn)M(a, -5)與點(diǎn)N(-2, b)關(guān)于X軸對(duì)稱，則a=_, b =_.( -4 , -7 )-25xyODABC(3, 5)(3, 5)(3, 5)(3, 5)(1)點(diǎn)A與點(diǎn)D有什么位置關(guān)系？點(diǎn)B與點(diǎn)C呢？點(diǎn)A與點(diǎn)D關(guān)于y軸對(duì)稱，點(diǎn)B與點(diǎn)C關(guān)于y軸對(duì)稱；(2)關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)有什么特征？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)相同。歸納：關(guān)于y軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)是:橫坐標(biāo)互為相反數(shù),縱坐標(biāo)相等.練習(xí):1、點(diǎn)P(-5, 6)與點(diǎn)Q關(guān)于y軸對(duì)稱，則點(diǎn)Q的坐標(biāo)為_.2、點(diǎn)M(a, -5)與點(diǎn)N(-2, b)關(guān)于y軸對(duì)稱，則a=_, b =_.( 5 , 6 )2-5新知?dú)w納“

3、關(guān)于坐標(biāo)軸對(duì)稱的點(diǎn)”的坐標(biāo)特征：在直角坐標(biāo)系中，點(diǎn)（a,b）關(guān)于X軸的對(duì)稱點(diǎn)是（a,-b)點(diǎn)（a,b）關(guān)于Y軸的對(duì)稱點(diǎn)是（-a,b）A（-,-1）3142-2-4-1-3012345-4-3-2-1C（-3,2）B（-1,-1）A（-,1）例1、如圖，利用關(guān)于坐標(biāo)軸對(duì)稱的點(diǎn)的坐標(biāo)的特點(diǎn)，分別作出ABC關(guān)于X軸和y 軸對(duì)稱的圖形。B（1,-1）C（3,2）A（,1）C（-3,-2）B（-1,1）例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=_.2a+b=83a=b+22a+b=-8-3a=b+2探索與創(chuàng)新 已知點(diǎn)Q(m,3),P(-