Simplify `cos 100^(@) cos 40^(@) +sin 100^(@) sin 40^(@)`

cos 70^(@) + sin 40^(@)=

Simplify : sin 100^(@) + cos 100^(@) .

( sin 70^(@) + cos 40^(@) )/( cos 70^(@) + sin 40^(@))=

(sin 70^(@) + cos 40^(@))/(cos 70^(@) + sin 40^(@))=

(sin 70^(@) + cos 40^(@))/(cos 70^(@) + sin 40^(@))=

sin 70^@ - cos 40^(@) =

(sin 70^(@) + cos 40^(@))/(cos 70^(@) + sin 40^(@)) =

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

cos70^(@)+sin40^(@)=