Вычислить sin(67)*sin(53)-cos(67)*sin(37)

Question

Вычислить
sin(67)*sin(53)-cos(67)*sin(37)

Answer 1

Sin53=sin(90-37)=cos37
sin67*cos37-cos67*sin37=sin(67-37)=sin30=1/2

Answer 2

Sin67°sin53°-cos67°sin37°=
sin67°sin53°-cos67°sin(90°-53°)=
sin67°sin53°-cos67°cos53°=
-(cos(67°+53°))=-cos120°=
1/2.