`piltalpha-betalt3pi`,`sinalpha+sinbeta=-21/65`,`cosalpha+cosbeta="-27/65`,then `cos((alpha-beta)/2)=` (A) `-6/65` (B) `-3/sqrt(130)` (C) `3/sqrt(130)` (D) `6/65`

pi

Let alpha and 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 (a) -3/(sqrt(130)) (b) 3/(sqrt(130)) (c) 6/(25) (d) 6/(65)

Le alpha and beta be such that pi

If cosalpha=3/5 and cosbeta=5/13 then cos^2((alpha+beta)/2)=16/65

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

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

If cosalpha+cosbeta=0=sinalpha+sinbeta , then cos2alpha+cos2beta=?

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

If cosalpha+cosbeta=0=sinalpha+sinbeta, then prove that cos2alpha+cos2beta=-2cos(alpha+beta) .

If cosalpha+cosbeta=0=sinalpha+sinbeta" then "cos2alpha+cos2beta