- Before 2D
- What is 2D shape?
- Circle
- Triangle
- Square
- Rectangle
Before 2D
Before 2D shape, let's go to 0 Dimensional shape and 1 Dimensional shape. The 0 Dimensional shape is less likely a shape when we look at it. Example of 0D (0 Dimensional) shape:
The 1D shape is like a line, a straight line or squiggly line or any form of line. It is 1D shape because the beginning of the line did not meet with the end of line. Below is the transition from 1D to 2D shape:
It is not 2D shape until the beginning of the line meet the end of the line.
What is 2D shape?
The 2D shape, also called as polygon, is made out of line or lines that connected to each other until it is appeared in closed shape. Means that 2D shape comprised of line or lines that connected from the beginning of line(s) to end of line(s).The 2D shape can be smooth with no point(s) like a circle, and also can be pointy like triangle, square, parallelogram, quadrilateral, rectangle, pentagon, hexagon and so on. Below are the example of 2D shapes:
Circle
Circle is the shape that we find at the objects such as tyre, coin, bottle cap and the letter o. The circle did not have points and no sides. The circle has circumference around it, and the centre of the circle is called origin. The length between origin and circumference line is called radius, while 2 radius are called diameter. Below is the picture of tyre from this website about Toyota Raize by Blauda:
Next, below is the picture that explains origin, circumference, radius and diameter:
The black circle is the circumference, blue line is radius, red dot is origin and green line is diameter.
Next, let's go to the pi (π). What is π? π is the ratio of circumference length of a circle (C) by the diameter of the circle (d or 2r, r is radius). Every circle has the same π value, which is 3.142.
The circumference (C) of the circle equals to π multiply by 2 radius. The circumference considered as the perimeter of the circle.
The image above shows the example of calculation of circumference. The circumference for circle above is 12.568 cm.
Next, to know the area of circle. Area (A) is the calculated size for the shape, or the space that available inside the shape. The area for the circle is π multiply by radius, then multiply by radius.
Triangle
Triangle is the shape that has 3 sides and 3 points. It also has width or breadth, and height. Below is the image of triangles:
To calculate the perimeter of a triangle, we must consider the total length of all sides.
The perimeter (P) of the triangle above is 21 cm. Each side of the triangle is 7 cm.
The area (A) of triangle is height multiply by breadth multiply by half. Why multiply by half? it is because triangle is considered half to the area of four-sides shape, be it square or rectangle.
Based on the image above, the breadth is length of left to right point of the triangle. The area (A) of the triangle is 27.41 cm².
Square
A square is a shape that has 4 sides and 4 points, and each side is in same length. The square also looks straight, because all angles are 90 degrees. Below is a picture of square:
To calculate the parameter, add all length of sides.
The parameter (P) of the square above is 20 cm.
To calculate the area of the square, multiply breadth (b) with height (h).
The area (A) of the square above is 25 cm².
Rectangle
The rectangle is same as square, but the different is the breadth of rectangle is longer than the height (or length) of rectangle. Rectangle has 4 sides and 4 points. Below is the image of rectangle:
The perimeter (P) of rectangle above is 38 cm.
To calculate the area (A), the height (length) of rectangle is multiplied by breadth of rectangle.
The area (A) of the rectangle above is 78 cm².
That's all for the 2D shapes. Any idea, please comment it here. Thank you!
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