Question

sin20°+sin13°*sin57°-sin33°*sin77°
как решить помогите.

Answer 1

sin20°+sin(90-77)sin57°-sin(90-57)sin77°=
sin20°+cos77°sin57°-cos57°sin77°=sin20°+sin57°*cos77°-cos57°*sin77°=sin20°+sin(57°-77°)=sin20°-sin20°=0