Question

Помогите решить, не шарю алгебру

Answer 1

Ответ:

$A(-2;-1)\ \ ,\ \ \ r=|OA|\ \ ,\ \ |OB|=2\ \ ,\ \ |AB|=|OC|=1\\\\r=\sqrt{2^2+1^2}=\sqrt5\\\\sin\alpha =sin(180^\circ +\angle AOB)=-sin\angle AOB=-\dfrac{|AB|}{r}=-\dfrac{1}{\sqrt5}\\\\cos\alpha =cos(180^\circ +\angle AOB)=-cos\angle AOB=-\dfrac{|OB|}{r}=-\dfrac{2}{\sqrt5}\\\\tg(180^\circ +\angle AOB)=tg\angle AOB=\dfrac{|AB|}{|OB|}=\dfrac{1}{2}$