The area 积分

思路就是用顶点式求抛物线的方程，然后再再求出其原函数，积分减去梯形面积即可

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #include <math.h>
 4 
 5 double a, b, c,  x1, x2, x3, p1, p2, p3;
 6 
 7 double  fun (double  x )
 8 { 
 9     return (1.0 / 3 ) * a * ( x - x1 ) * (x - x1 ) * (x - x1 ) + p1 * x; 
10 }
11 
12 int main( )
13 {
14     int T, i;
15     scanf("%d", &T);
16     while (T--) 
17     { // printf("%d\n",T);
18     
19         scanf("%lf %lf %lf %lf %lf %lf",&x1, &p1, &x2, &p2, &x3, &p3);
20         a = (p2 - p1) /( (x2 - x1) * (x2 - x1) );
21         b = (p2 + p3 ) * ( x3 - x2 ) /  2.0;
22         c = fun ( x3 ) - fun ( x2 ) - b;
23         printf("%.2lf\n",c);
24         //system("pause");
25     }
26     return 0;
27 }

　　

转载于:https://www.cnblogs.com/tangcong/archive/2011/07/20/2111341.html