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  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. #define ll long long
  6. #define ull unsigned ll
  7. #define ld long double
  8. typedef vector<int> vi;
  9. typedef multiset<int> mi;
  10. typedef multiset<ll> mll;
  11. typedef vector<ll> vll;
  12. typedef vector<bool> vb;
  13. typedef vector<string> vs;
  14. typedef set<ll> sll;
  15. typedef vector<vector<int>> _2vi;
  16. typedef vector<vector<ll>> _2vll;
  17. #define all(v) ((v).begin()), ((v).end())
  18. #define sz(v) ((ll)((v).size()))
  19.  
  20. #define vinp(v, n)                \
  21.     for (ull i = 0; i < (n); i++) \
  22.     cin >> (v)[i]
  23. #define printv(v)      \
  24.     for (auto i : (v)) \
  25.     cout << i << " "
  26. #define fr0(i, n) for (ull(i) = 0; (i) < (n); (i)++)
  27. #define fr1(i, n) for (ull(i) = 1; (i) < (n); (i)++)
  28. #define fr(i, x, n) for (ull(i) = (x); (i) < (n); (i)++)
  29. #define _CRT_SECURE_NO_WARNING
  30. const ll MOD = 1000000007;
  31.  
  32. void Bustany() {
  33.     ios_base::sync_with_stdio(false);
  34.     cin.tie(NULL);
  35.     cout.tie(NULL);
  36. }
  37.  
  38. const ll N = 1e5 + 5;
  39. vector<sll> adj(N);
  40. //_2vll adj(N,vll(N));
  41. vb vis;
  42.  
  43. void solve() {
  44.     ld a, b, c, d;
  45.     freopen("angle2.in", "r", stdin), freopen("angle2.out", "w", stdout);
  46.     cin >> a >> b >> c >> d;
  47.     ld x = (a * c) + (b * d);
  48.     ld y = sqrt((a * a) + (b * b)) * sqrt((c * c) + (d * d));
  49.     cout << fixed << setprecision(6) << acos(x / y) << endl;
  50. }
  51.  
  52. int main() {
  53.     Bustany();
  54.     ll t = 1;
  55. //     cin >> t;
  56.     while (t--) {
  57.         solve();
  58.     }
  59. }
Success #stdin #stdout 0.01s 7768KB
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https://ideone.com/OOMqCo
language:
C++ (gcc 8.3)
created:
19 days ago
visibility:
public

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