cos 1° cos 2° cos 3° ... cos 180° We know that cos 90° = 0 cos 1° cos 2° cos 3° ..........cos 90° .............. cos 180° cos 1° cos 2° cos 3° ..........(0).............. cos 180° When 0 is multiplied with anything it is always '0' Hence, option B is the correct answer.