16 \cos(20) \cos(40) \cos(60) \cos(80) = 1

Question

16 \cos(20) \cos(40) \cos(60) \cos(80) = 1

Answer 1

16 cos20 cos40 cos60 cos80=8 cos20cos40cos80=8cos20cos40cos80sin20/sin20=4sin40cos40cos80/sin20=2sin80cos80/sin20= sin160/sim20=sin(180-20)/sin20=sin20/sin20=1соs60=1/2