Question

(sin111°-2cos159°+cos(-90°))/cos21°

Answer 1

$frac{sin 111^{circ}-2cos 159^{circ}+cos(-90^{circ})}{cos21^{circ}}=frac{sin(90^{circ}+21^{circ})-2cos(180^{circ}-21^{circ})+cos90^{circ}}{cos21^{circ}}=\ \ =frac{cos21^{circ}-2cdot(-cos21^{circ})+0}{cos^{circ}}= frac{cos21^{circ}+2cos21^{circ}}{cos21^{circ}}=frac{3cos21^{circ}}{cos21^{circ}}=3$

Ответ: 3