lf `sinalpha-sinbeta=a` and `cosalpha+cos beta=b`, then write the value of `cos (alpha+ beta)`

If sinalpha-sinbeta=a and cosalpha+cosbeta=b then write the value of "cos"(alpha+beta) .

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

If sin alpha.sinbeta - cos alpha.cos beta+1=0 , then find the value of cot alpha.tan beta .

sin alpha=sinbeta, cos alpha=cos beta then

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 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

If alpha and beta satisfy sinalpha cos beta=-1/2 , then the greatest value of 2cos alpha sin beta is ……….

sin alpha+sinbeta=(1)/(4) and cos alpha+cos beta=(1)/(3) the value of sin(alpha+beta)