Let `alpha, beta` be such that `pi lt alph-betalt3piif sin alpha+sinbeta=-21/65and cos alpha+cos beta =-27/65,` then the value of
`cos""(alpha-beta)/(2),` is

Let alpha, beta be such that pi lt alpha-betalt3pi if sin alpha+sinbeta = -21/65 and cos alpha+cos beta = -27/65 , then the value of cos(alpha-beta)/(2) is

Let alpha,beta be such that pi lt alpha-beta lt3 pi . If sin alpha+ sin beta=(-21)/65 and cos alpha+ cos beta=(-27)/65 , then the value of cos((alpha-beta)/2) is

Let alpha, beta be such that pi lt=alpha lt=beta lt=3pi if sinalpha + sinbeta = -21/65 and cosalpha + cosbeta = -27/65 , then the value of cos""(alpha - beta)/65 is :

Let alpha, beta" such that "pi lt alpha-beta lt 3pi." If sin "alpha+sin beta=-21//65 cos alpha+cos beta=-27//65 , then find the value of cos ""(alpha-beta)/(2) .

Let alpha,beta be such that piltalpha-betalt3pi . If sinalpha+sinbeta=-(21)/(65)andcosalpha+cosbeta=-(17)/(65) , then the value of cos.(alpha-beta)/(2) is :

Let alphaandbeta be such that piltalpha-betalt3pi . If sinalpha+sinbeta=-(21)/(65)and cosalpha+cosbeta=-(27)/(65) , then the value of "cos"((alpha-beta))/(2) is

Let alpha, beta be such that it pi < alpha - beta <3 pi . if sin alpha + sin beta =-21/65 and cos alpha+cos beta = -27 / 65 then the value of cos ((alpha-beta)/2) is

Let alpha, beta be such that it pi < alpha - beta <3 pi . if sin alpha + sin beta =-21/65 and cos alpha+cos beta = -27 / 65 then the value of cos ((alpha-beta)/2) is

Let alpha,beta be such that pi<(alpha-beta)<3pi . If sinalpha+sinbeta=-21/65 and cosalpha+cosbeta=-27/65 , then the value of cos((alpha-beta)/2) is