let W(x) =∫_(−∞) ^(+∞) ((arctan(xt^2 ))/(2+t^2 ))dt
1) find a explicit form of f(x)
2) find the value of ∫_(−∞) ^(+∞) (t^2 /((2+t^2 )(1+x^2 t^4 )))dt .
let f_n (t)=t^(n−1) sin(nθ) with t from[0,1[ and θ from [0,π[
1) prove the uniform convergence of Σ f_n (t) on [0,1[
2) let S(t)=Σ f_n (t) calculate ∫_0 ^1 S(t)dt.