desparti in doua
si ai
doua integrale, una x/(x²+1) si 1/(x²+1)
aia cu x la numarator ii formezi derivata lu numitor (x²+1)'=2x
deci 1/2*integrala 2x/(x²+1) si care e formula directa ln(x²+1) intre 0 si 1
si cealalta, 1/(x²+1) e formula arctg x intre 0 si 1
