Question

Определите знак произведения: а)cos 20 sin 100 б)tg 500 cos 120 в)sin(-50) ctg 200 г)ctg(-60) tg 150 д)sin(-70) tg(-50) е)cos(-95) tg(-170)

Answer 1

$cos20\cdot sin10\ \textgreater \ 0\\\\sin(-50)\cdot ctg200=-sin50\cdot ctg200\ \textless \ 0\\\\sin(-70)\cdot tg(-50)=sin70\cdot tg50\ \textgreater \ 0\\\\tg500\cdot cos200=tg140\cdot cos200\ \textgreater \ 0\\\\ctg(-60)\cdot tg150=-ctg60\cdot tg150\ \textgreater \ 0\\\\cos(-95)\cdot tg(-170)=-cos95\cdot tg170\ \textless \ 0$