How to express the area of ​​a circle in C language

In C language, pi can be expressed by the constant π, and the area formula of a circle is πr², where r is the radius of the circle. The steps to calculate the area of ​​a circle are as follows: Define the radius r. Get the radius value. Calculate the area of ​​a circle using the constant π or the approximate value 3.14159.

How to express the area of ​​a circle in C language

In C language, you can use the constant π to express pi value (approximately 3.14159). The formula for the area of ​​a circle is πr², where r is the radius of the circle.

Steps:

1. Define the radius r: You can use the double data type to declare a variable to store radius. For example: double radius;
2. Get the value of the radius: You can enter the radius value through the keyboard or get the radius value from other programs. For example: printf("Please enter the radius of the circle:"); scanf("%lf", &radius);
3. Calculate the circle area: use #define macro to define the π constant, or use the approximate value 3.14159 directly. Then, calculate the area using the following formula: area = PI * radius * radius;

Sample code:

#include <stdio.h>
#include <math.h> // 包含 math.h 以使用 M_PI

int main() {
    double radius;
    printf("请输入圆的半径：");
    scanf("%lf", &radius);

    // 使用 M_PI 常量（更准确）
    double area = M_PI * radius * radius;

    printf("圆的面积为：%lf\n", area);

    return 0;
}

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