1+cos56 + cos 58 - cos 66 is equal to (A) 2 cos 28 cos 29 cos 33 (B)4 cos - Maths - Trigonometry

Question

1+cos56 + cos 58 - cos 66 is equal to
(A) 2 cos 28 cos 29 cos 33
(B)4 cos 28 cos 29 sin 33
(C) 4 cos 28 cos 29 cos 33
(D) 2 cos 28 cos 29 sin 33
(all angles ae in degree)

please tell me the way to deal like this problems

Manbar Singh · Accepted Answer

1 + cos 56° + cos 58° - cos 66°=1 - cos 66° + cos 56° + cos 58°=2 sin2 33° + 2 cos56°+58°2 cos 58°-56°2=2 sin2 33° + 2 cos 57° 
 cos 1°=2 sin2 33° + 2 cos90°-33° 
 cos90°-89°=2 sin2 33° + 2 sin 33° 
 sin 89°=2 sin 33°sin 33° + sin 89°=2 sin 33° 2 sin 33°+89°2 cos 89°-33°2=2 sin 33°2 sin 61° 
 cos 28°=4 cos 28° sin 61° sin 33°=4 cos 28° sin90°-29° sin 33°=4 cos 28° 
 cos 29° sin 33°

1+cos56 + cos 58 - cos 66 is equal to(A) 2 cos 28 cos 29 cos 33(B)4 cos 28 cos 29 sin 33(C) 4 cos 28 cos 29 cos 33(D) 2 cos 28 cos 29 sin 33(all angles ae in degree) please tell me the way to deal like this problems

1+cos56 + cos 58 - cos 66 is equal to
(A) 2 cos 28 cos 29 cos 33
(B)4 cos 28 cos 29 sin 33
(C) 4 cos 28 cos 29 cos 33
(D) 2 cos 28 cos 29 sin 33
(all angles ae in degree)

please tell me the way to deal like this problems