2cos75*sin75= 6-sin^2α-cos^2α= (-1+sin^2α)*tg^2α 1-tg67*tg7/tg67-tg7=

1)sin150=sin(180-30)=sin30=1/2
2)6-(sin²a+cos²a)=6-1=5
3)-cos²a*sin²a/cos²a=-sin²a
4)cos74/cos67*cos7:sin60/cos67*cos7=cos74/cos67*cos7*cos67*cos7/sin60=
cos74:√3/2=2cos74/√3=(2√3cos74)/3
По формулам:
1-tgatgb=cos(a+b)/cosacosb
tga-tgb=sin(a-b)/cosacosb