cos 1° cos 2° cos 3°…. cos 179° cos 180°
= cos 1° × cos 2° × cos 3° × .....× cos 90° × ..... × cos 179°

As we know,

cos 90° = 0

So,
= cos 1° × cos 2° × cos 3° × .....× 0 × ..... × cos 179°
= 0

As, cos 90° has the value 0 that’s why the whole answer will be zero.