Introduction to rectangle:
A rectangle, also called a rectangle, is a plane figure and a parallelogram with right angles. A rectangle is also defined as a parallelogram with four corners at right angles. A square is a special rectangle with four sides of the same length.
The essence of a rectangle is: two diagonal lines are equal; Two diagonal lines are equally divided; Two groups of opposite sides are parallel respectively; The two groups of opposite sides are equal respectively; All four corners are right angles; There are two symmetrical axes (there are four squares); Unstable (easily deformed); The square of the diagonal length of a rectangle is the sum of the squares of both sides; The quadrilateral obtained by connecting the midpoints of the sides of the rectangle in turn is a diamond.
Perimeter introduction:
The length integral of the edge around a finite area is called the perimeter, which is the length of a graph. The perimeter of a polygon is also equal to the sum of all sides of a graph, the perimeter of a circle =πd=2πr(d is the diameter, R is the radius, π), and the perimeter of a sector = 2R+nπR÷ 180? (n= central angle) =2R+kR(k= radian).
Content standard:
The understanding of perimeter is the learning content of the third grade in the first phase of compulsory education mathematics (Volume I). The learning content of "understanding of perimeter" in the curriculum standard actually includes three levels: first, let students know the concept of perimeter and experience it in real life; Secondly, let students master the method and process of measuring circumference; Finally, experience and feel the application of mathematics in life.
Course objectives:
The curriculum standard clearly points out the target requirement of "knowing the perimeter", that is, "pointing out and measuring the perimeter of specific figures, exploring and mastering the perimeter formulas of rectangles and squares".
In addition, in the overall goal of mathematics curriculum, "get some preliminary mathematical practical experience and be able to use the knowledge and methods learned to solve simple problems;" Feeling the role of mathematics in daily life "is also the goal requirement of" knowing the perimeter ".
The course objectives here are actually the refinement and concrete embodiment of knowledge and skills, mathematical thinking, problem solving and emotional attitude objectives. These goals involve the following requirements of the "learning goals" in the first learning period: "skills to obtain preliminary measurements (including estimates)" in the knowledge and skills goals;
The goal of mathematical thinking is to "develop the concept of space in the process of exploring the shape, size, positional relationship and movement of simple objects and figures"; On the goal of solving the problem, "there are different solutions to understand the same problem." Experience in solving problems with peers. Initially learn to express the general process and results of solving problems ";
As well as the goal of emotion and attitude, "with the encouragement and help of others, I am curious about things related to mathematics around me and can actively participate in vivid and intuitive mathematics activities." Feel the close connection between mathematics and daily life. Rationality of mathematical thinking processes such as observation, operation and induction. Under the guidance of others, mistakes in mathematical activities can be found and corrected in time. "