Question

please say the answer fast

Answer 1

sin 20.sin 40.sin 60.sin 80
=cos 60×.sin 40×.0.86 ×sin 80
=0.5×0.86×0.86×0.984
=0.3638832

Answer 2

I am consedring that you know all the compound angles .

For ex

2cosAsinB=sin(A+B)-sin(A-B)