" (ii) "4(cos^(3)20^(@)+cos^(3)40^(@))=3(cos20^(@)+cos40^(@))

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

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

4cos^(3)40^(@)-3sin50^(@)=

cos20^(@)cos40^(@)cos60^(@)cos80^(@)=

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

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

Cos^(2)20^(@)+Cos^(2)40^(@)+cos^(2)80^(@)=

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 60^(@) * cos 80^(@) =

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