Question

ПОМОГИТЕ С АЛГЕБРОЙ

Дано: ctg(п/2 +t)=2корень из6

Найти: cos(п+t)

Answer 1

$Ctg(\frac{\pi }{2}+t)=2\sqrt{6}\\\\Cg(\frac{\pi }{2}+t)=-tgt\\\\-tgt=2\sqrt{6}\\\\tgt=-2\sqrt{6} \\\\1+tg^{2}t=\frac{1}{Cos^{2}t} \\\\Cos^{2}t=\frac{1}{1+tg^{2}t }=\frac{1}{1+(-2\sqrt{6})^{2}} =\frac{1}{1+24}=\frac{1}{25}\\\\Cos(\pi+t)=-Cost=-\sqrt{Cos^{2}t }=-\sqrt{\frac{1}{25}}=-\frac{1}{5}=-0,2$