Question

$\cos 1^o\cos 2^o\cos 3^o..........\cos 1{80}^o$

Answer 1

$\cos 1^{\circ }.\cos 2^{\circ }.\cos 3^{\circ }.\cos 4^{\circ }.........\cos {90}^{\circ }........\cos {178}^{\circ }.\cos {179}^{\circ }.\cos {180}^{\circ }$

$\cos {90}^{\circ }=0$

when anything is multilpied to 0 the result is always

$socos1.cos2.cos\mathrm{3........}cos180=0$