Given that sin α + cos β = one third, sin β - cos α = one half, find the value of COS (α + β) Sin α - sin β = one third cos α + cos β = one half

Given that sin α + cos β = one third, sin β - cos α = one half, find the value of COS (α + β) Sin α - sin β = one third cos α + cos β = one half

(sina+sinb)²+(cosb-cosa)²=(1/3)²+(1/2)²
(sin²a+2sinasinb+cos²b)+(cos²b-2cosacosb+cos²a)=13/36
2-2cos(a+b)=13/36
cos(a+b)=59/72