第二单元

Unit 2

Pattern beauty -- symmetry, translation and rotation

二 图案美——对称、平移与旋转

Lesson 1

What questions can you ask?

你能提出什么问题？

Cooperative exploration

合作探索

1. What are the features of these figures?

1. 这些图形有什么特点？

They're both symmetric figures.

它们都是对称图形。

If you fold it in half, the two sides will be exactly on each other.

如果从中间对折，两边会完全重合。

Fold a figure in half along a straight line, if the two sides of the line can be exactly the same, such a figure is called axisymmetric figure.The line where the crease is is called its axis of symmetry.

将图形沿着一条直线对折，如果直线两侧的部分能够完全重合，这样的图形叫做轴对称图形。折痕所在的这条直线叫做它的对称轴。

Which of the shapes we've learned are axisymmetric? Can you figure out their axis of symmetry?

我们学过的哪些图形是轴对称图形？你能找出它们的对称轴吗？

These figures are all axisymmetric figures

这些图形都是轴对称图形

长方形：rectangle        正方形： square

三角形： triangle         梯形： trapezoid

By folding in half, I found that the rectangle has two axes of symmetry.

通过对折我发现长方形有两条对称轴。

A square has four axes of symmetry.

正方形有4条对称轴。

2. Can you draw the other half of the figure below to make it axisymmetric?

2. 你能画出下面图形的另一半，使它成为轴对称图形吗？

I first find several important points on the graph, and then find the symmetry points of these points according to the distance from each point to the axis of symmetry.
我先从图形上找到几个重要的点，再根据每个点到对称轴的距离找到这些点的对称点。

At last connect the dots.

最后把这些点连起来。

Lesson 2

◆◆◆◆◆    卐

What questions can you ask?

你能提出什么问题？

Cooperative exploration

合作探索

1. ◆◆◆◆◆How did you get it?

1. ◆◆◆◆◆是怎样得到的？

We can do it by translation.

可以用平移的方法。

A graph translation, to determine the direction, and then......

将一个图形平移时，要先确定方向，再......

2. 卐How did you get it?

2. 卐是怎样得到的？

It's given by rotation.

是通过旋转得到的。

If you think about it, what are some of the things that you should pay attention to when you rotate the graph?

想一想，旋转图形时要注意哪些问题？