第四单元

Unit four

Little craftsmen - understanding polygons

巧手小工匠——认识多边形

Lesson One

第一课

Why triangles?

为什么做成三角形的？

What other questions can you ask?

你还能提出什么问题？

Why triangles?

1.为什么做成三角形的？

I guess the triangle is more stable.进入翻译页面

我猜三角形比较稳固。

Let's do an experiment to find out.

我们做个实验来研究一下吧。

A quadrilateral deforms when it is pulled.

四边形一拉就变形。

No matter how you pull the triangle, it won't move.

三角形怎么拉也拉不动。

Triangles have stability.

三角形具有稳定性。

Do you know triangles?

2.你认识三角形吗？

Three line segments are joined end to end to form a figure called a triangle.

三条线段首尾相接，围成的图形叫做三角形。

The line between the vertex and the perpendicular foot is called the height of the triangle, and the opposite side is called the base of the triangle.

从三角形的一个顶点到它的对边做一条垂线，顶点和垂足之间的线段叫做三角形的高，这条对边叫做三角形的底。

Can you classify triangles?

3.你能把三角形分类吗？

So let's do that with a piece of triangle paper.

我们利用三角形纸片来研究一下。

You can look at it from both sides and angles.

可以从边和角两个方面来研究。

I studied the angles of triangles and found...

我研究了三角形的角，发现…

A triangle whose three angles are acute

三个角都是锐角的三角形

A triangle whose Angle is a right Angle

有一个角是直角的三角形

A triangle that has an obtuse Angle

有一个角是钝角的三角形

I measured the sides of a triangle and found that some triangles have two sides equal......

我量了三角形的边，发现有的三角形，两条边相等......

I measured the angles of triangles and found that some triangles have two angles equal......

我量了三角形的角，发现有的三角形有两个角相等......

A triangle whose sides are equal is an isosceles triangle. The base angles of an isosceles triangle are equal.

两条边相等的三角形是等腰三角形，等腰三角形的底角相等。

A triangle with three equal sides is an equilateral triangle (also called an equilateral triangle).

三条边相等的三角形是等边三角形（也叫正三角形）。

The angles of an equilateral triangle are equal.

等边三角形的三个角相等。

Lesson Two

第二课

Why can't you circle a triangle?

怎么围不成三角形呢？

What other questions can you ask?

你还能提出什么问题？

Can any three sticks form a triangle?

1.任意的三根小棒，能围成一个三角形吗？

My three sticks can form a triangle

我的三根小棒能围成一个三角形。

Why can't I put my three little sticks?

我的三根小棒怎么摆不成呢？

What is the relationship between the three sides of a triangle?

三角形的三条边之间有什么关系呢？

The sum of the lengths of any two sides of a triangle is greater than the third.

三角形任意两边长度的和大于第三边。

What is the sum of the three interior angles of a triangle?

2.三角形三个内角的和是多少度？

The sum of the angles of a triangle is 180 degrees.

三角形的内角和是180度。

Lesson Three

第三课

I made a coat hanger out of strips of wood

我用木条做衣架。

I made a little easel out of wooden strips

我用木条做个小画架

What questions can you ask?

你能提出什么问题？

What shape is the hanger? What are its characteristics?

1.衣架是什么形状的？它有哪些特征？

Its shape is a parallelogram.

它的形状是平行四边形。

Where do parallelograms exist in life?

生活中哪里还有平行四边形？

There is a parallelogram on the electric telescopic door at the school gate.

学校大门口的电动伸缩门上有平行四边形。

There are parallelograms on the fence

篱笆上也有平行四边形。

On the banister...

楼梯扶手栏杆上…

The characteristics of a parallelogram can be studied from both sides and angles.

平行四边形的特征可以从边和角两方面来研究。

A parallelogram is a quadrilateral in which two sets of opposite sides are parallel

两组对边分别平行的四边形叫平行四边形。

The segment of a perpendicular line from a point on one side of the parallelogram to its opposite side is called the height of the parallelogram

从平行四边形一条边上的一点到它对边的垂直线段叫做平行四边形的高

The opposite side is the base of the parallelogram.

这条对边是平行四边形的底。

What is the shape of a trapezoid? What are its characteristics?

2.梯形是什么形状？它有哪些特征？

There is no trapezoid in life.

生活中哪里还有梯形。

There are trapezoids on the basketball court.

篮球场上有梯形。

There are also trapezoids on the jump box.

跳箱上也有梯形。

The wing of a model airplane...

飞机模型的机翼…

The characteristics of research question types can be considered from two aspects: edge and corner.

研究题型的特征可以从边和角两方面来思考。

It's a quadrilateral with four sides. There are four horns

它是一个四边形，有4条边。有4个角。

A set of quadrilaterals with only opposite sides parallel is called a trapezoid.

只有一组对边平行的四边形叫做梯形。

A trapezoid with two equal waists is called an isosceles trapezoid

两腰相等的梯形叫做等腰梯形。

The vertical segment from a point on one of the base edges of the trapezoid to its opposite side is called the height of the trapezoid.

从梯形一条底边上的一点到它对边的垂直线段叫做梯形的高。

Density of graphics

图形的密铺

There are many secret phenomena in our life. Do you know the secret of them?

生活中有许多密铺现象，你知道其中的奥秘吗？

So let's look at that.

我们来研究一下吧。

research contents

研究内容：

1. What is dense paving and which plane graphics can be dense paving? Which ones can't?

1，什么是密铺，哪些平面图形能密铺？哪些不能？

2. How to close it? How to design the pattern?

2，怎样密铺？如何设计密铺图案？

Research method: refer to materials to understand the relevant content of the secret shop.

研究方式：查阅资料，了解有关密铺的相关内容。

Activity requirement: Team division of labor and cooperation, each person to choose a graph for research

活动要求：小组分工合作，每人选择一种图形来进行研究。

Prepare materials, scissors, rulers, cardboard, and colored pens.

准备材料，剪刀，尺子，卡纸，彩笔。

Triangles, parallelograms, trapezoids and hexagons can be packed separately.

三角形、平行四边形、梯形、正六边形能单独密铺。

A circle and a regular pentagon cannot be packed separately.

圆和正五边形不能单独密铺。