数学 ACdream 1196 KIDx's Triangle

题目传送门

 /*
     这道题花了好长时间AC，思路有，但是表达式少写了括号一直乱码,囧!
     注意：a==0时要特判:)
 */
 #include <cstdio>
 #include <algorithm>
 #include <iostream>
 #include <cstring>
 #include <string>
 #include <cmath>
 using namespace std;

 const int MAXN = 1e4 + ;
 const int INF = 0x3f3f3f3f;
 const double PI = acos (-1.0);

 double f(double k)
 {
     return 1.0 * k * PI / ;
 }

 int main(void)        //ACdream 1196 KIDx's Triangle
 {
     //freopen ("H.in", "r", stdin);

     double a, b, c, d;
     double ae, cd, ce, de, ab, ad, be, bd;
     double x;
     while (scanf ("%lf%lf%lf%lf", &a, &b, &c, &d) == )
     {
         if (a == )
         {
             puts ("0.00");    continue;
         }

         ad = sin (f(c)) / sin (f(a+b+c));
         ae = sin (f(c+d)) / sin (f(b+c+d));
         be = sin (f(b)) / sin (f(b+c+d));
         bd = sin (f(a+b)) / sin (f(a+b+c));
         de = sqrt (be*be + bd*bd -  * be * bd * cos (f(d)));

         x = acos ((de*de+ae*ae-ad*ad) / (2.0 * de * ae)) *  / PI;

         if (x < )    printf ("%.2f\n", 180.0 - x);
         else    printf ("%.2f\n", x);
     }

     return ;
 }