Question

Leaving this up before I sleep (nearly 2 now got school xD)
Would appreciate if someone could give an explanation on doing this...
\[\large \lim_{n \rightarrow \infty} \cos 1 \times \cos \frac{ 1 }{ 2 } \times \cos \frac{ 1 }{ 4 } \times \cos~ ... \cos \frac{ 1 }{ 2^n }\]