`4(cos^3 20^(@) + cos^(3) 40^(@))=`

if ( cos ^(3) 20^@ + cos^(3) 40^(@))/( cos 20^@+ cos 40^(@)) = k ,then the value of k is

cos^(3) 20^(@) + cos^(3) 100^(@) + cos^(3) 140^(@) =

Prove that, 4 (cos^(3) 10^(@) + sin^(3) 20 ^(@))=3 (cos 10^(@) + sin 20^(@))

4( cos^(3) 10^(@) + sin^(3) 20^(@))=

8 cos^(3) 20^(@) -6 cos 20^(@) =

i) Prove that: cos^(3)2A+3cos2A = 4(cos^(6)A-sin^(6)A) ii) Prove that: 4(cos^(3)10^(@) + sin^(3)20^(@)) = 3(cos10^(@)+sin20^(@))

cos 20^(@) cos 40^(@) cos 80^(@)=

Prove that 4(cos ^(3) 10^(@) + sin ^(3) 20^(@)) = 3 ( cos 10^(@) + sin 20^(@)).

If (cos^(3)20^(0)+cos^(3)40^(0))/(cos20^(0)+cos40^(0))=k , then the value of k is

Prove that (sin20^(@) + sin40^(@)) + (cos20^(@) + cos40^(@))=(sqrt(3)+1)cos10^(@)