L'aire \( A = \pi r^2 = 3,14 \times 5^2 = 3,14 \times 25 = 78,5 \) cm².

["Understanding the Area of a Circle: A Simple Guide Using ( A = \pi r^2 = 3,14 \ imes 5^2 = 78,5 , \ ext{cm}^2 )", "Calculating the area of a circle is one of the most fundamental concepts in geometry—and it’s simpler than you might think. This article breaks down how to compute the area using the formula ( A = \pi r^2 ), including an easy example with ( r = 5 , \ ext{cm} ), resulting in ( A = 78,5 , \ ext{cm}^2 ).", "### What Is the Area of a Circle?", "The area represents the total space enclosed within the boundary of a circle. This metric is essential in fields like engineering, architecture, physics, and everyday applications such as landscaping and manufacturing.", "### The Area Formula: ( A = \pi r^2 )", "The formula to find the area of a circle involves:\n- ( A ): area in square centimeters (cm²)\n- ( \pi ) (pi): a mathematical constant approximately equal to 3,14 (or ( 3.1416 ) for greater precision)\n- ( r ): the radius—the distance from the center of the circle to its edge", "### Step-by-Step Calculation with ( r = 5 , \ ext{cm} )", "1. Identify the radius:\n Given ( r = 5 , \ ext{cm} )", "2. Apply the formula ( A = \pi r^2 ):\n [\n A = \pi \ imes (5)^2 = \pi \ imes 25\n ]", "3. Substitute ( \pi \approx 3,14 ):\n [\n A = 3,14 \ imes 25\n ]", "4. Perform the multiplication:\n [\n 3,14 \ imes 25 = 78,5\n ]", "So, the area is ( A = 78,5 , \ ext{cm}^2 ).", "### Why Use 3,14 for ( \pi )?", "Using 3,14 is a practical approximation of ( \pi ), which is an irrational number with infinite decimal places. While precise calculations use ( \pi \approx 3.14159265 ), 3,14 offers a quick and widely accepted estimate—perfect for classroom learning and everyday problems.", "### Visualizing the Formula", "Imagine dividing a circle into hundreds of tiny sectors like slices of a pie. The more slices you take (i.e., the more segmented your circle becomes), the closer your area approximation gets to the exact value of ( \pi r^2 ). This intuitive idea lies behind the elegant formula used today.", "### Real-World Applications", "Knowing how to calculate the area of a circle helps solve practical problems:", "- Determining the surface area for painting or coating circular objects (pans, pipes, wheels)\n- Calculating space requirements in gardens or floorings\n- Designing mechanical parts requiring rotational symmetry", "### Summary", "- Radius ( r = 5 , \ ext{cm} )\n- Formula: ( A = \pi r^2 )\n- Calculation: ( 3,14 \ imes 25 = 78,5 , \ ext{cm}^2 )\n- Result: The area enclosed by the circle is 78,5 cm²", "Whether you’re a student brushing up on geometry basics or a professional calculating material needs, mastering the area of a circle is a valuable skill. Remember: ( A = \pi r^2 ), with ( \pi ) approximately 3,14, can compute area efficiently and accurately in everyday situations.", "---", "Keywords: area of a circle, formula ( A = \pi r^2 ), calculate circle area, circumference and area, geometry basics, how to find circle area, circle area with radius 5 cm, ( 3,14 \ imes 25 = 78,5 \ ext{cm}^2 )"]