`cos52^(@) + cos68^(@) + cos172^(@)=`

The value of cos 52^(@) + cos 68^(@) + cos 172^(@) is

Statement I: cos 52^(@)+cos68^(@)+cos172^(@)=1/2 Statement II: 4sin Acos^(3)A-4cosAsin^(3)A=cos4A Which of the above statements is correct?

The value of cos 52^@ + cos 68^@ + cos 172^@

The value of cos 52^@ + cos 68^@ + cos 172^@ is:

Prove that cos32^(@) sin20^(@) + cos144^(@) cos2^(@) + sin68^(@) cos56^(@) = 0

A=cos20^(@)cos40^(@)cos60^(@)cos80^(@),B=cos60cos42^(@)cos66^(@)cos78^(@) and C=cos36^(@)cos72^(@)cos108^(@)cos144^(@) then

A=cos 20^(@)cos 40^(@) cos60^(@)cos 80^(@) , B=cos6^(@)cos42^(@)cos66^(@)cos78^(@) and C=cos 36^(@)cos72^(@)cos 108^(@)cos 144^(@) then