数学七年级下：《变化的鱼》ppt课件(共26张PPT)

数学七年级下：第七章平面直角坐标系育才学校陈华萍123456780–1–2–3–4–512345图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的横坐标保持不变，将各坐标的纵坐标都减１，则原图型变为什么样？yx原图形被向下平移1个单位图中的“鱼”是由原来的“鱼”怎样变化而来得到的？它们对应“顶点”的坐标有怎样的关系？123456780–1–2–3–4–512349105在直角坐标系中描出以下各点：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)并用线段依次连接,看一看是什么图案.yx图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的纵坐标保持不变，将各坐标的横坐标变成原来的２倍会得到什么？则坐标变化为：原图形被横向拉伸2倍(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(2x,y)(0,0)(10,4)(6,0)(10,1)(10,-1)(6,0)(8,-2)(0,0)123456780–1–2–3–4–512349105图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的纵坐标保持不变,将各坐标的横坐标变成原来的1/2，图形会怎么变？则坐标变化为：yx原图形被横向压缩1/2(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(x/2,y)(0,0)(2.5,4)(1.5,0)(2.5,1)(2.5,-1)(1.5,0)(2,-2)(0,0)–4123456780–1–2–361234578910xy图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的如果横坐标保持不变，纵坐标变成原来的２倍，那么所得图案又会发生什么变化?原图形被纵向拉伸２倍–4123456780–1–2–361234578910xy图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的如果横坐标保持不变，纵坐标变成原来的½，那么所得图案又会发生什么变化?原图形被纵向压缩1/212345-1-2-30–1–2–3–4–51234-4-55图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的yx想一想与原图形关于y轴对称将各坐标的纵坐标保持不变，横坐标都乘以－１，图形会变成什么样？则坐标变化为(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(-x,y)(0,0)(-5,4)(-3,0)(-5,1)(-5,-1)(-3,0)(-2,-2)(0,0)123456780–1–2–3–4–512345图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的将各坐标的纵坐标都乘以－1，横坐标保持不变，则图形怎么变化？坐标变化为yx与原图形关于x轴对称(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(x,-y)(0,0)(5,-4)(3,0)(5,-1)(5,1)(3,0)(4,2)(0,0)–4123456780–1–2–361234578910xy1.图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的如果横坐标与纵坐标同时乘以２，那么所得图案又会发生什么变化?原坐标变为：原图形被横向、纵向各拉伸2倍原图形的形状没变，面积是原来的4倍。(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(2x,2y)(0,0)(10,8)(6,0)(10,2)(10,-2)(6,0)(8,-4)(0,0)–4123456780–1–2–361234578910xy如果横坐标乘以２再减去1，纵坐标不变，那么所得图案会发生什么变化?延伸一、平移1.纵坐标不变，横坐标分别增加（减少）a个单位时，图形平移a个单位；2.横坐标不变，纵坐标分别增加（减少）a个单位时，图形平移a个单位；向右（向左）向上（向下）二、伸长（压缩）3.纵坐标不变，横坐标分别变为原来的a倍，则图形为原来的a倍（a1）4.横坐标不变，纵坐标分别变为原来的a倍，则图形为原来的a倍（a1）5.横坐标与纵坐标同时变为原来的a倍，则图形为原来的a倍（a1）…横向伸长或图形横向压缩为原来的a倍（0a1）。纵向伸长或图形纵向压缩为原来的a倍（0a1）。纵、横向同时伸长三、轴对称6.纵坐标不变，横坐标分别乘-1，所得图形与原图形关于；7.横坐标不变，纵坐标分别乘-1，所得图形与原图形关于；Y轴对称X轴对称123410432–2–1–1–2–3–4–3–4123410432–2–1–1–2–3–4–3–4与左图三角形相比，右图中的三角形发生了怎样变化。右图中的直角三角形顶点的坐标发生怎样变化。123410432–2–1–1–2–3–4–3–4123410432–2–1–1–2–3–4–3–4与左图三角形相比，右图中的三角形发生了怎样变化。右图中的直角三角形顶点的坐标发生怎样变化。123410432–2–1–1–2–3–4–3–4123410432–2–1–1–2–3–4–3–4123410432–2–1–1–2–3–4–3–4与左图三角形相比，右图中的三角形发生了怎样变化。右图中的直角三角形顶点的坐标发生怎样变化。123410432–2–1–1–2–3–4–3–4123410432–2–1–1–2–3–4–3–4与左图三角形相比，右图中的三角形发生了怎样变化。右图中的直角三角形顶点的坐标发生怎样变化。导学案【中考真题】–5图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的将各坐标的纵坐标与横坐标都乘以－1，图形会变成什么样？yx234510–1–2–3–412345–1–2–3–4–5原坐标变为(0,0)(-5，-4)(-3,0)(-5,-1)(-5,1)(-3,0)(-4,2)(0,0)与原图形关于原点中心对称(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(-x,-y)(0,0)(-5,-4)(-3,0)(-5,-1)(-5,1)(-3,0)(-4,2)(0,0)123456780–1–2–3–4–512349105在直角坐标系中描出以下各点：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)并用线段依次连接，看一看是什么图案。yx123456780–1–2–3–4–512349105图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的则坐标变化为纵坐标保持不变，将各坐标的横坐标加２又会怎样？yx原图形被向右平移2个单位(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(x+2,y)(2,0)(7,4)(5,0)(7,1)(7,-1)(5,0)(6,-2)(2,0)123456780–1–2–3–4–512349105图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的则坐标变化为：纵坐标保持不变，将各坐标的横坐标减２，图案会变成什么样？yx-1-2原图形被向左平移2个单位(x,y)(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)(x-2,y)(-２,0)(3,4)(1,0)(3,1)(3,-1)(1,0)(2,-2)(-2,0)123456780–1–2–3–4–512345图中的鱼是将坐标为：(0,0)(5,4)(3,0)(5,1)(5,-1)(3,0)(4,-2)(0,0)的点用线段依次连接而成的横坐标保持不变，将各坐标的纵坐标都加２，则原图型变为什么样？yx原图形被向上平移2个单位123410432–2–1–1–2–3–4–3–4123410432–2–1–1–2–3–4–3–4与左图三角形相比，右图中的三角形发生了怎样变化。右图中的直角三角形顶点的坐标发生怎样变化。