(cos80°-sin70°)/(cos40°+sin50°)=? помогите....

Question

(cos80°-sin70°)/(cos40°+sin50°)=?

помогите....

Answer 1

1. cos(90°-10°)-sin70°=sin10°-sin70°=2sin(-30°)cos40°=-cos40°

2. cos40°+sin(90°-40°)=cos40°+cos40°=2cos40°

3. -cos40°/(2cos40°)=-1/2=-0,5