Tổng hợp kiến thức hình chữ nhật đầy đủ chi tiết nhất

The rectangle is a special quadrilateral, as well as a basic and popular type of geometry today. To better understand the knowledge of this geometry, let’s refer to the details in the following article with Nguyễn Tất Thành.

What is a rectangle?

Of all the shapes in mathematics, a rectangle (hcn) is known as a special quadrilateral with 4 right angles, or it is a parallelogram with one right angle.

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Rectangular properties

• Rectangles have most of the properties of parallelograms and isosceles trapezoids

• The two rectangular diagonals intersect and are equal at the midpoint of each line, as well as forming 4 isosceles triangles.

• Inscribed in a circle whose center is the center of the figure.

Rectangular identification sign

To be able to recognize a rectangle, people can rely on the following characteristics:

• A quadrilateral with three right angles is a rectangle.

• An isosceles trapezoid with one right angle is a rectangle.

• A parallelogram with one right angle is a rectangle.

• A parallelogram with two equal diagonals is a rectangle.

Other definitions related to rectangles

In a rectangle, in addition to the above characteristics, there are still some related definitions that everyone needs to understand as follows:

Diagonal of a rectangle

Definition: This is the line connecting two opposite vertices of the figure. Each rectangle will have 2 equal diagonals.

Nature:

Formula to calculate diagonal of a rectangle: c = a2 + b2 => c = √a2 + b2

In there:

• c is the diagonal of the square.

• a, b are the sides of the square.

Rectangular axis of symmetry

Definition: A straight line is the axis of symmetry of a figure when axial symmetry passes through that line, transforming the figure into itself. For a rectangle, the main axis of symmetry is 2 straight lines passing through the midpoint of each pair of opposite sides of the shape, so each shape will have 2 lines of symmetry.

Properties: The two parts of hcn divided by the axis of symmetry are similar.

Center of rectangular symmetry

A point is considered the center of symmetry of a shape if the symmetry of that center transforms the shape into itself, the intersection of two diagonals is the center of symmetry of the hcn.

The circumcircle circumscribes hcn

• The circle passing through the vertices of the rectangle will be called the circumcircle of the figure.

• Each rectangle will have only one circumcircle.

Formulas related to rectangles

In knowledge about rectangles, children will have to clearly understand the formulas for calculating the corresponding perimeter and area to solve the exercises accurately. Specifically:

Formula to calculate circumference of hcn

The perimeter of a rectangle is equal to 2 times the sum of the length and width: C = 2 x (a+b).

For example: Given rectangle ABCD, with a length of 7cm and a width of 5cm. Calculate the perimeter of that rectangle?

Solution:

The perimeter of rectangle ABCD is:

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(5 + 7) x 2= 24 (cm)

Answer: 24 cm

Formula to calculate the area of ​​a rectangle

Rectangles are known to have a simple way to calculate area, just taking the product of 2 adjacent sides.

Formula to calculate the area of ​​a rectangle:

S = ab

In there:

• a is the width of the rectangle.
• b is the length of the rectangle.

For example: Given rectangle ABCD, length is 5cm, width 4cm. What is the area?

Solution:

The area of ​​rectangle ABCD is:

5 x 4 = 20 (cm2)

Answer: 20 cm2

Common types of exercises about elementary school rectangles

In the elementary math program, children will learn and do the following types of exercises related to rectangles:

Form 1: Definition formula

This is a basic form of exercise, often included in multiple-choice exams that children will encounter. The main topic given is a theoretical question related to rectangles, requiring children to choose the correct answer corresponding to the question posed.

Therefore, to solve this exercise, children are required to clearly grasp the basic knowledge of shapes.

For example: Choose the best answer in the following sentences:

A. A rectangle is a quadrilateral with 4 equal sides.

B. A rectangle is a quadrilateral with 4 right angles

C. A rectangle is a quadrilateral with 2 right angles

D. Both A, B, and C are wrong.

==> Answer: B. Because by definition, a rectangle is a shape with 4 right angles.

Form 2: Calculate the perimeter of a rectangle

This is also a basic type of exercise that your baby will also become familiar with. With this exercise, children need to master the formula for calculating the perimeter of a shape, C = 2 x (a+b), combined with the given data to solve the exercise correctly.

For example: Given rectangle ABCD, with length 5cm, width 3cm. Calculate the perimeter of the corresponding shape?

Solution:

The perimeter of rectangle ABCD is:

C = 2 x (a + b) = 2 x (5 + 3) = 16 cm.

Answer: 16cm

Form 3: Calculate the area of ​​a rectangle

Similar to the problem of calculating the perimeter above, in the exercise of calculating the area of ​​a small rectangle, the formula S = axb will be applied to find the correct answer.

For example: A rectangular piece of cardboard is 7 cm wide and 10 cm long. Calculate the area of ​​that piece of cardboard.

Solution: The area of ​​the cardboard is: 7 x 10 =70 (cm2)

Math exercises related to rectangles for children to practice

Based on the above theoretical knowledge, let’s apply it to solve some of the following exercises:

Exercise 1: Choose the most correct answer among the following?

A. A rectangle is a quadrilateral with four equal sides.

B. A rectangle is a quadrilateral with four right angles.

C. A rectangle is a quadrilateral with two right angles.

D. All of the above options are incorrect.

Exercise 2: Find the wrong sentence in the following sentences

A. In a rectangle there are two equal diagonals.

B. In a rectangle, there are two diagonal lines that intersect at the midpoint of each line.

C. In a rectangle, two adjacent sides are equal.

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D. In a rectangle, the intersection of the two diagonals is the center of the rectangle

Lesson 3: Which of the following signs is not recognized correctly?

A. A parallelogram with two diagonal lines intersecting at the midpoint of each line is a rectangle.

B. A quadrilateral with three right angles is a rectangle.

C. An isosceles trapezoid with one right angle is a rectangle.

D. A parallelogram with two equal diagonals is a rectangle.

Exercise 4: Circle the incorrect option

A. In a right triangle, the median line corresponds to the hypotenuse and is half the hypotenuse.

B. In a triangle, if the median line is equal to one side and is half that side, then the triangle is a right triangle.

C. In a right triangle, the median line corresponding to the side of the right angle is not equal to that side.

D. In a right triangle, the median line corresponding to the hypotenuse is perpendicular to the hypotenuse.

Lesson 5: In a rectangle, the dimensions are 5cm and 12cm respectively. What is the length of the diagonal of the rectangle?

A. 17cm

B. 13cm

C. √ 119 cm

D. 12cm

Lesson 6: The area of ​​a rectangle with length 12cm and width 8cm is:

Lesson 7: The area of ​​a rectangle with length 3dm and width 17cm is:

Lesson 8: A rectangular garden is 36cm long and 1/4 the width of the length. The area of ​​the rectangle is:

Lesson 9: A rectangle has a width of 12cm and an area of ​​96cm². The length of the rectangle is:

Problem 10: A rectangular piece of land is 34m long and 26m wide. Calculate the perimeter of that land.

Lesson 11: A rectangular picture frame has a perimeter of 8m and a length of 3m. Calculate the width of that picture frame.

Lesson 12: A rectangular schoolyard has a perimeter of 50m, the length is 4 times the width. Calculate the length and width of that school yard.

Lesson 13: Given a rectangle with a width of 7cm and a length twice the width. Calculate the half-perimeter of the above rectangle.

Problem 14: A rectangular piece of land is 35m long and 20m wide. Calculate the perimeter of that land.

Lesson 15: A rectangle has a perimeter of 160m and a length of 50m. What is the width of the rectangle?

The secret to helping children learn and remember rectangular knowledge effectively

Knowledge about rectangles for elementary school children is really too difficult or has many complicated exercises, but it is an important foundation. Therefore, to help your children learn this knowledge firmly, parents should not ignore the following tips:

Create excitement and passion for learning math for children with Nguyễn Tất Thành Math

For children, to learn math effectively, it is necessary to create excitement and passion in them. However, many parents today often apply traditional teaching methods, which fail to create excitement and even create more pressure and fear of learning math in their children.

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Make sure your child masters basic knowledge about rectangles

To solve exercises about rectangles, children are required to master basic knowledge related to this geometry, typically definitions, properties, identifying signs, formulas for calculating perimeter and area. , types of exercises….

Because when children grasp this basic knowledge, they can really solve the exercises most accurately. Therefore, parents need to test their child’s knowledge regularly to avoid forgetting and promptly reinforce knowledge.

Practice with your child and practice regularly

Once your child has firmly grasped the knowledge and theory, parents should create conditions for their child to practice and practice regularly. Continuous practice will help children clearly understand the knowledge they learn, remember better, create excitement when learning and easily apply theory to solving exercises…

So, the practice here that parents can do with their children is to solve many exercises about rectangles, take examples related to practice, solve exam questions about geometry, and do similar activities. Collaborating with Nguyễn Tất Thành Math,…

Ask your child to read and understand the assignment

One of the important factors when doing math homework is to read the problem carefully. Therefore, parents should ask their children to read and understand what data and questions are given in the test so that they can come up with the correct solution and treatment plan.

Conclude

Above is basic knowledge information about rectangles. Although it is basic, it is an important foundation for learning more difficult knowledge later. Therefore, parents should guide and accompany their children to study to achieve the best results.

Nguồn: https://truongnguyentatthanh.edu.vn
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