Show that cos 24 + cos 55 + cos 125 + cos 204 + cos 300= 1/2 - Maths - Trigonometric Functions

Question

Show that cos 24 + cos 55 + cos 125 + cos 204 + cos 300= 1/2

Pia Vanave · Answer

(cos24+cos204)+(cos55 + cos125) +cos300 =
1/2
L H S
= (2cos112cos90) + (2cos90cos35) +
cos(360-60)
= (2cos112 0) + (2cos35 0) +cos60 [ bcoz cosx + cosy =
2cos(x+y)/2cos(x-y)/2 ] and [cos90 = 0]
= 0 + 0 + 1/2
= 1/2
= R H S
hence prOved