а) lim (1 - x)tg × π/2 × x б) lim (2x - 3)(ln (5x - 1) - ln (5x - 7)) .
x →1 × . x → + ∞ .
1-x=t
t → 0
x=t+1
tg((π/2)*x)=tg((π/2)*(t+1))=tg((π/2)t+(π/2))=-ctg((π/2)t)
=lim_(t → 0) t*(-ctg((π/2)t))= - lim_(t → 0) t/tg((π/2)t)=
=- lim_(t → 0)((π/2)t)/tg((π/2)t)* (1/(π/2))= [b]-2/π[/b]