Question

cos20 + cos40 + cos140 + cos 160

Answer 1

the answer is 0.9871927924

Answer 2

Answer:

The answer is 0.

Step-by-step explanation:

Given,

$cos 20^{\circ}+ cos 40^{\circ}+ cos 140^{\circ} + cos 160^{\circ}$

$=cos 20^{\circ}+ cos 40^{\circ} + cos ( 180 - 40 )^{\circ} + cos ( 180 - 20)^{\circ}$

$=cos 20^{\circ} + cos 40^{\circ} - cos 40^{\circ} - cos 20^{\circ}$

( Because, cos (180 - x) = - cos x )

$=0+0$

$=0$