NDA Maths Mock Test – 01 – Q44

What will be the value of cos 12^circ + cos 84^circ + cos 156^circ + cos 132^circ ?

• 3/4
• 2sqrt(5)
• -1/2
• -2sqrt(3)

‘ We ha√e, cos 12° + cos 84° + cos 156° + cos 13²° ‘
1 = (cos 12° + cos 13²°) + (cos 84° + cos 156°) 1
‘ _ 2cos( 124157 ) cos 212) 12 cos (S41) cos =
! 0 0 0 0 !
=2c0s 72″ cos 60° +2 cos 120″ cos 36
‘ =2 sin 18° cos 60° + 2 cos 120° cos 36°
1 _ 5-1) (1 -1 VBL) _ -1 !