`2 cos 75^(@) . Cos 15^(@)` बराबर है ।

cos 15^(@) - cos 75^(@) =

Cos15^(@) - Cos75^(@) =

Prove that (i) " sin " 80^(@) "cos " 20^(@) - " cos " 80^(@) " sin " 20^(@) =(sqrt(3))/(2) (ii) " cos " 45^(@) " cos " 15^(@) - " sin " 45^(@) " sin " 15^(@) = (1)/(2) (iii) " cos " 75^(@) " cos " 15^(@) + " sin " 75^(@) " sin " 15^(2)= (1)/(2) (iv) " sin " 40^(@) " cos " 20^(@) " + cos " 40^(@) " sin " 20^(@) =(sqrt(3))/(2) (v) " cos " 130^(@) " cos " 40^(@) l + " sin " 130^(@) " sin " 40^(@) =0

The value of cos 75^(@) cos 15^(@) is equal to

(sin 75^(@) - sin 15 ^(@))/( cos 75^(@) + cos 15 ^(@)) = (1)/(sqrt3)

Which one of the following number (s) is/are rational? - 1) sin 15^(@) 2) cos 15^(@) 3) sin 15^(@) cos 15^(@) 4) sin15^(@) cos 75^(@)

cos15^(@)-cos75^(@)=

sin 10^(@)+sin 20^(@) + sin 40 ^(@) + sin 50 = A) sin 15^(@) +sin 75^(@) B) cos 15^(@) + cos75^(@) C) sin 70^(@) + sin 80^(@) D) cos 70^(@) + cos 80^(@)