Verified answer

Ответ:

1)sin300°=sin(360°-60°)=(-π/3)=-√3/2

2)10*1/2+8*1/2=5+4=9

3)sin(125°+55°)=sin(180°)=0

4)2sin105°cos105°=sin2a=sin2*105°=sin210°=-1/2