" 4.Prove that ":cos A*cos(60^(@)+A)cos(60^(@)-A)=(1)/(4)cos3A

Prove that: (i) cos A cos(60^(@)-A)cos (60^(@)+A)=(1)/(4)cos 3A (ii) "tan" A+"tan"(60^(@)+A)-"tan"(60^(@)-A)=3 tan 3A .

Prove that: cosA. Cos(60^(@)+A)cos(60^(2)-A)=1/4 cos3A

Prove that cos(60^(@)+A) + cos(60^(@)-A)-cosA=0

Prove that: cos Acos(60^0-A)cos(60^0+A)=1/4cos3A

If A=30^(@) , show that : 4cosAcos(60^(@)-A)*cos(60^(@)+A)=cos3A

Prove that : cos Acos(60-A)cos(60+A)=1/4cos3A

Prove that cos 20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that :cos20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that cos20^(@)cos40^(@)cos60^(@)cos80^(@)=(1)/(16)

Prove that cos thetacos(60^(@)- theta)cos(60^(@)+theta) = 1/4 cos 3 theta