# 2 Dimensional Figures

## Understanding Two-Dimensional Figures in Math

When we think of the term 2D, our minds often jump to video games or movies. However, in mathematics, a two-dimensional figure is a shape formed by closed lines on a plane, with two key dimensions: length and width. Unlike three-dimensional objects, 2D figures do not have depth as they only exist in a two-dimensional space.

### Definition of Two-Dimensional Figures

Two-dimensional figures, also known as 2D figures, are flat shapes on a plane with two dimensions, length and width, on the same plane. For example, a triangle can be created by drawing three lines on a 2D surface, such as a piece of paper. While three-dimensional (3D) shapes have depth and require multiple planes to be represented, 2D figures can be easily defined with just one plane or surface.

**Examples of 2D Figures:**Triangle, Square, Rectangle, Circle

### Exploring Different Types of Two-Dimensional Figures

#### Triangle

A triangle is a 2D shape with three sides and three vertices. The sum of all the internal angles in a triangle is always 180º. Depending on the length of the sides and the angles formed, triangles can be classified into different types, such as equilateral, isosceles, and scalene triangles.

#### Square

Squares are 2D figures formed by four equal sides and four vertices. All the internal angles of a square are equal to 90º. It is important to note that in order for a shape to be classified as a square, all four sides must be of the same length.

#### Rectangle

Similar to squares, rectangles have four sides and four vertices. However, unlike squares, the length of each side may vary. The defining characteristic of a rectangle is that opposite sides have equal length. Like squares, all internal angles in a rectangle are also equal to 90º.

#### Circle

A circle is a 2D figure that consists of points equidistant from a center point. Unlike other 2D shapes, circles do not have vertices. The distance from the center to any point on the circle is called the radius, while the diameter is twice the length of the radius.

**Other Two-Dimensional Shapes:** hexagons, octagons, diamonds, and more. These shapes can be classified based on the number of sides, vertices, and their structure.

### Finding the Perimeter of 2D Figures

In mathematics, the perimeter of a 2D figure is the sum of all the sides' lengths. This can be calculated using the formula: **P = a1 + a2 + a3 + ... + an = ∑ani=1n**. The symbol ∑ indicates that the side lengths should be added up to find the perimeter.

#### Perimeter of a Triangle

The triangle, with three sides, has the simplest perimeter formula. The perimeter of a triangle is equal to the sum of all three sides.

## Perimeter Calculation in 2D Figures

Let's explore how to calculate the perimeter of various 2D shapes.

For example, an isosceles triangle in 2D has two equal sides and one different side. To find the perimeter, we use the formula: P = a + b + c, where a, b, and c are the lengths of the sides. If the triangle has side lengths of 3m, 3m, and 1m, the perimeter would be 7m.

Interestingly, even though triangles, squares, and rectangles are distinct shapes, we can still calculate their perimeters using the same formula. This applies to any 2D figure - simply add up all the side lengths to find the perimeter.

For squares and rectangles, we add up all four sides to calculate the perimeter. The perimeter of a square is a + a + a + a, where a is the length of each side. Similarly, the perimeter of a rectangle is a + a + b + b, where a and b are the different side lengths of the two opposite pairs. Let's look at some examples.

For instance, if Eva's whiteboard measures 46 cm by 60 cm, what would be its perimeter? Since the whiteboard has two different lengths and four sides, we know it is a rectangle. Thus, the perimeter would be 46 + 46 + 60 + 60 = 212 cm.

Moreover, if we have a 2D square figure with a side length of 25 cm, the perimeter would be calculated as a + a + a + a, which is 25 + 25 + 25 + 25 = 100 cm.

## Perimeter of a Circle

But how do we calculate the perimeter of circles? Unlike other shapes, we cannot use the perimeter formula because circles do not have sides. Instead, we use a different formula to calculate the perimeter (also known as circumference): P = 2πr, where r is the radius of the circle and π is a fixed value.

The relationship between the circumference and radius of a circle reveals that the perimeter of a circle increases as the radius increases. For example, if a circle has a diameter of 14 cm, we can find its perimeter by first calculating the radius, which is half the diameter. So, r = 14 cm / 2 = 7 cm. Then, we can use the formula P = 2π7 = 44 cm to determine the perimeter. In this case, the perimeter of the circle is 44 cm.

## Understanding the Area of 2D Figures

The area of a 2D figure is the space enclosed within its perimeter. We measure area using square units such as square meters (m^{2}) or square feet (ft^{2}). For instance, a room's floor can be seen as a 2D figure with the walls as its perimeter.

Depending on the shape of the 2D figure, there are different formulas to calculate its area.

### Calculating the Area of a Triangle

The formula for calculating the area of a triangle is A = 1/2bh, where b is the base of the triangle and h is the height, or the distance from the base to the opposite vertex. It's important to note that the base can be any side, not just the shortest one. In this case, the height is measured from the chosen base to the opposite vertex.

For example, if a triangle has a base of 13 inches and a height of 6 inches, its area would be: A = 1/2(13)(6) = 39 inches^{2}.

### Calculating the Area of Squares and Rectangles

The formula for finding the area of a square or rectangle is the same: A = bh. The only difference is that a rectangle has two different side lengths, while a square has all sides equal.

For any 2D figure with four parallel sides, the formula A = bh can be used to calculate its area.

## Understanding 2-Dimensional Figures

In mathematics, a 2-dimensional figure is a shape that exists in a plane surface and is formed by the union of three or more lines, also known as sides. This article will give you a comprehensive understanding of 2D figures and how to classify them.

#### Calculating the Area of a Square

To determine the area of a square, we can use the formula A = b^{2}, where b represents the length of any side. This formula also applies to other figures with all sides of equal length.

For example, if we have a tablecloth with dimensions 70 inches by 70 inches, we can find its area by plugging in the length of one side, which is b = 70 inches, into our formula.

Solution: A = b^{2} = (70)^{2} = 4900 square inches.

#### Calculating the Area of a Circle

Similar to the perimeter, the area of a circle also depends on its radius. We use the formula A = πr^{2} to calculate the area of a circle, where r is the radius and π is the constant pi. As the radius increases, the area of the circle also increases by the power of two.

For instance, imagine spinning a rope tied to a fixed point in a garden. This motion forms a 2D circle. As you increase the radius of the spinning rope, you will notice that the area of the circle also grows.

Let's try an example. Find the area of a circle with a radius of r = 5.2 cm, rounded to the nearest tenth.

Solution: A = πr^{2} = 3.14 x 5.2^{2} = 3.14 x (5.2 x 5.2) = 84.9056 ≈ 84.9 cm^{2}.

#### Different Types of 2D Figures

Apart from the commonly known shapes like the triangle, square, rectangle, and circle, there are countless other 2D figures categorized based on the number of sides, vertices, and internal angles formed by the vertices.

We can also extend the sides of a rectangle by one and create a pentagon, or by two and make a hexagon, and so on. Similarly, for four-sided figures, we have the rhombus, with two equal sides and non-90 degree angles.

#### Differences Between 2D and 3D Figures

The primary difference between 2D and 3D figures is the number of dimensions they possess. 2D figures only have length and width, while 3D figures also have height. Therefore, 2D figures can be placed on a 2D plane surface, while 3D figures require a 3D space to exist.

#### Key Takeaways

- 2D figures are shapes formed by three or more lines in a plane surface.
- They can be classified based on the number of sides, vertices, and internal angles.
- Calculating the area of a figure depends on its shape and can be found using different formulas.
- 2D figures only have two dimensions while 3D figures have three dimensions.The Importance of Understanding 2D and 3D Figures in Mathematics
- In the world of mathematics, having a solid understanding of 2D and 3D figures is crucial as they serve as the foundation for more complex concepts. These figures, also known as shapes, are composed of distinct geometric elements and are used to solve various mathematical problems.
- The Significance of 2D Figures
- 2D figures, also referred to as planar figures, are shapes that exist on a flat or two-dimensional plane and have only two dimensions - length and width. These figures are essential for calculating the perimeter and area of various shapes, such as squares, rectangles, and triangles. Understanding how to classify and measure the properties of these figures is crucial in solving more advanced mathematical equations.
- The Role of 3D Figures in Visualizing Objects
- In contrast, 3D figures, also known as solid figures, are objects that exist in a 3-dimensional space and have three dimensions - length, width, and depth. These figures provide a more realistic representation of objects, as they accurately depict their physical properties. For example, a cube is a 3D figure that has six square faces, representing its length, width, and height.
- Being able to visualize and manipulate 3D figures is essential in fields like architecture, engineering, and physics, where accurate measurements and representations are required. Moreover, understanding the properties and relationships between 3D figures helps in solving advanced geometric problems and equations.
- The Importance of 3D Space in Understanding 3D Figures
- One crucial aspect of 3D figures is their need for 3-dimensional space. In order to accurately represent these figures, they must be viewed and studied in a 3D space, which includes length, width, and height. This allows us to understand and analyze their dimensions and properties correctly. Without considering 3D space, it is not possible to visualize or manipulate 3D figures accurately.
- Conclusion
- In conclusion, having a thorough understanding of 2D and 3D figures is essential in mathematics. As 2D figures serve as the foundation for more complex concepts, and 3D figures accurately depict objects in a 3-dimensional space, both types of figures play crucial roles in solving mathematical problems. By knowing how to classify and measure the properties of these figures, one can solve more advanced mathematical equations with ease.