View Compilation Error

0_0_33473393_31839.cpp: In function 'int main()':
0_0_33473393_31839.cpp:18:35: error: 'cos' was not declared in this scope
   double vx = V * cos(a * pi / 180);//vx=cos x;vy=sin x;
                                   ^
0_0_33473393_31839.cpp:19:35: error: 'sin' was not declared in this scope
   double vy = V * sin(a * pi / 180);
                                   ^
0_0_33473393_31839.cpp:22:42: error: 'sqrt' was not declared in this scope
    t1 = 2 * ((vy / g) - (sqrt(vy * vy - g)/g));
                                          ^
0_0_33473393_31839.cpp:29:30: error: 'sqrt' was not declared in this scope
    t2 = (sqrt(vy * vy + 6 * g) - vy) / g;
                              ^