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十六夜喵夜

铁虫 (初入文坛)

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注册: 2014-03-15
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[求助] 为什么用曲边扇形公式编出来的求椭圆面积程式和标准答案不一样？

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>
#include<time.h>
#include<stdlib.h>
struct coordinate
{
double aerpa1[5];
double aerpa2[5];
double aerpa;
double r[5];
double x;
double y;
double a;
double b;
double gama;
double h;
double ai[5];
double s;
int n;
};
struct coordinate cd[626];
double fu(double x, int i, int j)
{
double Bt, aerpa3, aerpa4, xd, yd, res;
res = 0;
aerpa3 = 1;
aerpa4 = 1;
xd = aerpa3*(cd.a*cos(cd.aerpa)*cos(x) + cd.b*sin(cd.aerpa)*sin(x));
yd = aerpa4*(sin(x)*cos(cd.aerpa)*cd.b - sin(cd.aerpa)*cos(x)*cd.a);
res = xd*xd + yd*yd;
res = sqrt(res);
res = pow(res, 2.0);
return res;
}
double sguess(double xiaxian, double shangxian, int r, int l)
{
double x5[8] = { 0.9602898565 ,-0.9602898565,0.7966664774,-0.7966664774,0.5255354099,-0.5255354099,0.1834346425,-0.1834346425 };
double A5[8] = { 0.1012285363,0.1012285363,0.2223810345,0.2223810345,0.3137066459,0.3137066459,0.3626837834,0.3626837834 };
double * p, *t;
double g = 0;
int i;
p = x5;
t = A5;
for (i = 0; i<8; i++)
{
g = fu((shangxian - xiaxian)*p / 2 + (xiaxian + shangxian) / 2, r, l)*t + g;
}
g = ((shangxian - xiaxian) / 2)*g;
return g;
}
double S(int i)
{
int j;
double s, sp, a, b;
s = 0;
s = sguess(0, 2 * 3.141592654, 0, 1);
s = 0.5*s;
return s;
}
void generate(int i)
{
double PI = 3.141592654;
cd.a = 5;
cd.b = 0.5;
cd.n = 3;
cd.h = PI * 2 / cd.n;
cd.aerpa = 0;
cd.s = S(i);
}
void main()
{
generate(0);
printf("wucha=%lf,Sjisuan=%lf,Szhen=%lf\n", cd[0].s - 3.141592654*cd[0].a*cd[0].b, cd[0].s, 3.141592654*cd[0].a*cd[0].b);
}
最后的运算结果是b越小误差越大，有的时候误差可以达到37（计算值）-0.7（真实值）的差距，但是圆一定不存在误差