28." If "sin alpha=(1)/(2)," prove that "(3cos alpha-4cos^(3)alpha)=0

If sin alpha =(1)/(2) , prove that (3 cos alpha - 4 cos ^(3) alpha )=0.

sin alpha-cos alpha=(1)/(3) then sin^(4)alpha-cos^(4)alpha=

If alpha = (pi)/(13), Prove that cos alpha cos 2alpha cos 3alpha cos 4alpha cos 5alpha cos 6alpha = (1)/(64) .

If cos alpha+cos beta=(1)/(3) and sin alpha+sin beta=(1)/(4) prove that cos[(alpha-beta)/(2)]=+-((5)/(24))

If y = (2 sin alpha )/(1 + cos alpha + sin alpha) then, prove that (1 - cos alpha + sin alpha)/(1 + sin alpha) = y .

cos(alpha-beta)+cos(beta-gamma)+cos(gamma-alpha)=-(3)/(2), prove that cos alpha+cos beta+cos gamma=sin alpha+sin beta+sin gamma=0

(sin 5 alpha-sin3alpha)/(cos 5 alpha+2 cos 4 alpha+cos 3alpha)=

If (cos^4 alpha)/(cos^2beta)+(sin^4alpha)/(sin^2beta)=1 ,then prove that (cos^4beta)/(cos^2alpha)+(sin^4beta)/(sin^2alpha)=1

If (cos^4 alpha)/(cos^2 beta)+ (sin^4 alpha)/(sin^2 beta) =1 , prove that : (cos^4 beta)/(cos^2 alpha)+ (sin^4 beta)/ (sin^2 alpha) =1 .

If alpha = pi/3, prove that cos alpha*cos 2alpha*cos 3alpha*cos 4alpha*cos 5alpha*cos 6alpha = -1/16.