А)2sinπ/6cosa+2cosπ/6sina-√3sina=2*1/2sina+2*√3/2sina-√3sina=sina+√3sina-√3sina=
=sina
б)(sinacosb+cosasinb)(sinacosb-cosasinb)+sin²b=sin²acos²b-cos²asin²b+sin²b=
=sin²acos²b+sin²b(-cos²a+1)=sin²acos²b+sin²bsin²a=sin²a(cos²b+sin²b)=sin²a
в)(sinacosb+cosasinb-2sinacosb)/(2cosacosb-cosacosb+sinbsina)=
=(cosasinb-sinacosb)/(cosacosb+sinbsina)=sin(b-a)/cos(b-a)=tg(b-a)