Question

ctg40° * tg140°
Должно получиться (-1)

Answer 1

Ответ:

ctg40∗tg140=ctg40∗tg(180−40)=ctg40∗(−tg40)=−1

Answer 2

$ctg40^{\circ}\cdot tg140^{\circ}=ctg30^{\circ}\cdot tg140^{\circ}=ctg40^{\circ}\cdot tg\left ( 180^{\circ}-40^{\circ} \right )=-\frac{1}{tg40^{\circ}}\cdot tg40^{\circ}=-1$