数学 ACdream 1196 KIDx's Triangle

 1 /*
 2     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!
 3     注意：a==0时要特判:)
 4 */
 5 #include <cstdio>
 6 #include <algorithm>
 7 #include <iostream>
 8 #include <cstring>
 9 #include <string>
10 #include <cmath>
11 using namespace std;
12 
13 const int MAXN = 1e4 + 10;
14 const int INF = 0x3f3f3f3f;
15 const double PI = acos (-1.0);
16 
17 double f(double k)
18 {
19     return 1.0 * k * PI / 180;
20 }
21 
22 int main(void)        //ACdream 1196 KIDx‘s Triangle
23 {
24     //freopen ("H.in", "r", stdin);
25 
26     double a, b, c, d;
27     double ae, cd, ce, de, ab, ad, be, bd;
28     double x;
29     while (scanf ("%lf%lf%lf%lf", &a, &b, &c, &d) == 4)
30     {
31         if (a == 0)
32         {
33             puts ("0.00");    continue;
34         }
35 
36         ad = sin (f(c)) / sin (f(a+b+c));
37         ae = sin (f(c+d)) / sin (f(b+c+d));
38         be = sin (f(b)) / sin (f(b+c+d));
39         bd = sin (f(a+b)) / sin (f(a+b+c));
40         de = sqrt (be*be + bd*bd - 2 * be * bd * cos (f(d)));
41 
42         x = acos ((de*de+ae*ae-ad*ad) / (2.0 * de * ae)) * 180 / PI;
43 
44         if (x < 0)    printf ("%.2f\n", 180.0 - x);
45         else    printf ("%.2f\n", x);
46     }
47 
48     return 0;
49 }