<span>sin 30>0</span>
<span>cos(-30)>0</span>
<span>tg(-45)<0</span>
<span>ctg60>0</span>
{x-y=1⇒x=1+y
{xy=6
y²+y-6=0
y1+y2=-1 U y1*y2=-6
y1=-3⇒x1=1-3=-2
y2=2⇒x2=1+2=3
(-2;-3);(3;2)
y(x) = (4x^2 + 3) * tg x
производная произведения: (f(x)*g(x)) = f'(x)*g(x) + g'(x)*f(x)
y ' (x) = 8x*tgx + (4x^2 + 3)/cos²x