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

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 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 :

If sinalpha+sinbeta=a ,cosalpha+cosbeta=b=>sin(alpha+beta) =

sinalpha+sinbeta=a ,cosalpha+cosbeta=b=>sin(alpha+beta)

If sinalpha+sinbeta=a and cosalpha+cosbeta=b prove that: cos(alpha-beta)=((a^2+b^2-2)/2)

If sinalpha+sinbeta=a and cosalpha+cosbeta=b prove that: cos(alpha-beta)=((a^2+b^2-2)/2)

If cosalpha+cosbeta=2/3 and sinalpha+sinbeta=2/5 then find the vvalue of tan((alpha+beta)/2)

If sinalpha+cosbeta=5/4 and cosalpha+sinbeta=3/4 , then value of sin(alpha+beta)=?

If sinalpha+sinbeta=1//2 and cosalpha+cosbeta=sqrt(3)//2 then 3beta+alpha =