Let ` alpha , beta ` be such that `pi lt alpha - beta lt 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 lt alpha lt beta lt 3pi, 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 -beta lt 3 pi. If sin alpha + sin beta =- (21)/(65) and cos alpha + cos beta =- (27)/(65) and if the value of cos "" (alpha - beta)/(2) =(-a)/(sqrtb), then a xx b=

Let alpha, beta be such that pi lt alpha- beta lt 3pi . 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-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 pi lt alpha- beta lt 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

If alpha, beta be such that pi < alpha- beta < 3 pi . If sin alpha +sin beta= -21/65 and cos alpha + cos beta = -27/65 , then the value of cos frac (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