b=βcos(2a+b)=cos(a+b)cosa-sinasin(a+b)=1/3-sinasin(a+b)cos(a+b)=1===>a+b=2kπb=2kπ-acosb=cos(2kπ-a)=cosa=1/3sinb=-sinacos2a=cos(4kπ-2b)=cos2b=2cos^2b-1=-7/91-sin^2a=1/9sin^2a=8/9sina=±2√2/3sinas...