(sin 9') * (sin 69') + (sin 81') * (sin21') = ? (sin 9') * (cos 21') + (cos 9') * (sin 21') Как дальше решать ? -_-'( ' - градус)

Question

(sin 9') * (sin 69') + (sin 81') * (sin21') = ? (sin 9') * (cos 21') + (cos 9') * (sin 21') Как дальше решать ? -_-'( ' - градус)

(sin 9') * (sin 69') + (sin 81') * (sin21') = ? (sin 9') * (cos 21') + (cos 9') * (sin 21') Как дальше решать ? -_-' ( ' - градус)

Гость

Ответ(ы) на вопрос:

Accepted Answer

(sin 9') * (sin 69') + (sin 81') * (sin21')=(sin 9') * (sin 69') + (cos 9') * (cos 69')=cos(69-9)=cos60=1/2 (sin 9') * (cos 21') + (cos 9') * (sin 21')=sin(9+21)=sin30=1/2