1)Г
2)cos(83-23)=cos60=1/2 Б
3)-2sin(-a)sin2a=2sinasin2a Г
4)
А)cosa=-√1-16/25=-√9/25=-3/5 2
Б)tga=4/5:(-3/5)=-4/5*5/3=-4/3 1
В)sin2a=2*(-3/5)*4/5=-24/25 3
5)sin240=sin(180+60)=-sin60=-√3/2
6)cos105=√((1+cos210)/2)=√((1+cos(180+30)/2)=√((1-cos30)/2)=√(1-√3/2)/2)=
(1/2-√3/4)
7)(cos3acos2a-sin3asin2a)/sin2acos2a)*1/2cos5acos4a= cos5a/sin2acos2a)*1/2cos5acos4a=2/sin4acos4a=4/sin8a
8)(4sin²acos²a-4sin²a)/(4sin²acos²a+4sin²a-4sin²a-4cos²a)= 4sin²a(cos²a-1)/4cos²(sin²a-1)=4sin²a*(-sin²a)/4cos²a*(-cos²a)=-4sin^4a/-4cos^4a=tg^4a
9)sin2π/9*cos2π/9*cos4π/9*cos8π9/sin2π/9=1/2sin4π/9*cos4π/9*cos8π9/sin2π/9=
1/4sin8π/9*cos8π9/sin2π/9=sin16(π/8)/8sin(2π/9)=sin(2π-2π/9)/8sin(2π/9)= -sin(2π/9)/8sin(2π/9)=-1/8