Question

Determinaţi primitiva F(x) a funcţiei f:R→R, f(x)= 1/(1+9x^2 ) ce verifică condiţia F(1/3)=0.

Answer 1

F(x)=∫dx/(1+9x²)=1/9∫dx/(1/9+x²)=1/9∫dx/[(1/3)^2+x²]=
1/9*1/(1/3)arctgx/(1/3)+c=1/9*3arctg3x+c=1/3arctg3x+c
f(1/3)=1/3arctg3*1/3+c=0
1/3*arctg1+c=0
1/3*π/4+c=0
π/12+c=0
c=-π/12

Answer 2

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