1. cos(a+b)cos(a-b)+sin(a+b)*sin(a-b) 2. tg(a+b)-tgb/1+tg(a+b)tgb 3. cos(a-п/6)-0,5sina

1
cos(a+b)cos(a-b)+sin(a+b)*sin(a-b)=cos(a+b-a+b)=cos2b
2
(tg(a+b)-tgb)/(1+tg(a+b)tgb)=tg(a+b-b)=tga
3
cos(a-п/6)-0,5sina=cosacosπ/6+sinasinπ/6-0,5sina=
=√3/2*cosa+0,5sina-0,5sina=√3/2*cosa