1) sin 240°+ cos(-210°) 2) sin 330°+ cos(-300°)

1) sin 240 + cos(-210) = sin 240 - cos 210 = sin(180 + 60) - cos(180 + 30)=
= - sin 60 + cos 30 = - sgrt3/2 + sgrt3/2 = 0;

2) sin 330 + cos (-300) = sin(360 - 30) + cos (-360 + 60) = sin (-30) + cos 60 =
= - sin 30 + cos 60 = -  1/2   + 1/2   = 0.

1) sin240⁰+cos(-210⁰)=sin(270⁰-30⁰)+cos210⁰=-cos30°+cos(270°-60°)=-√3/2-sin60°=-√3/0-√3/2=-√3

2) sin330°+cos(-300°)=sin(270°+60°)+cos300°=-cos60°+cos(270°+30°)=-cos60°+sin30°=-0.5+0.5=0