604. The area of the circle
The formula for calculating the area of a circle is defined as A=πR^2.
Please use this formula to calculate the area of the given circle.
The value of π is 3.14159.
Input format
The input contains a floating point number, which is the radius of the circle R.
Output format
The output format is "A=X", where X is the area of the circle, expressed as a floating point number with four decimal places.
data range
0<R<10000.000
Input sample:
2.00
Sample output:
A=12.5664
Idea code:
//这道题我用float就没有通过，99%的情况直接用double就好（除非遇到了空间限制题）
#include <cstdio>
int main()
{
double pi = 3.14159, r;
scanf("%lf",&r);
printf("A=%.4lf\n", pi * r * r);
return 0;
}