1, the long side of a rectangle is called length and the short side is called width.

2, and the horizontal plane in the same direction is called long, and vice versa. The length and width of a rectangle are relative, and it cannot be absolutely said that "it is longer than the width", but it is customary to say that the long one is long and the short one is wide.

The definition of rectangle perimeter is put forward on the basis of students' preliminary understanding of rectangle. In teaching, we should be good at guiding students to observe, induce and summarize, and cultivate students' ability.

The formula for calculating the circumference of a rectangle is the focus of this lesson, and the teacher should focus on it. Students should not only remember the content of the formula, but also know how the formula is derived. Derivation formula: rectangle circumference = length+width+length+width.

On this basis, a model is put forward to inspire students to find out the law by observing and asking questions, so as to get the formula of rectangle circumference: (length+width) X2.

Extended data:

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.

(1) The two diagonals are equal.

(2) Two diagonal lines are equally divided.

(3) Two groups of opposite sides are parallel respectively.

(4) The two groups of opposite sides are equal respectively.

Baidu encyclopedia-rectangle