a) f'(3)= lim x-3 (2^x-2³)/(x-3)= lim x-3 [2³( 2^(x-3) -1) / (x-3) ] = 2³ · ln 2
b) x -> π/4 ( scadem π/4)
=> x- π/4 -> 0 , x-π/4 = y ⇒ x= y+ π/4
lim y- 0 [sin(y+π/4) - sin π/4] / (y+π/4 - π/4) =
=lim y-0 [ sin y + sin π/4 - sin π/4] / y=
=lim y-0 (sin y)/ y = 1