Question

find the value of cos 80 cos 40 cos20 Cos 30​

Answer 1

Answer:

COS 40 degree . COS 80 degree = root3/16.

Answer 2

Answer:

cos80 cos 40 cos 20

cos20[cos(60-20)cos(60+20)]

cos20[cos2 60-sin2 20]=cos20

[1upon4-sin2 20]

1upon4 cos 20 {1-4(1-cos2 20)}