let v_n (a)= ∫_(1/n) ^n (1−(a/x^2 ))arctan(1+(a/x))dx with a>0
1) determine a explicit form of v_n (a)
2) study the convergence of Σ_n v_n (a)
3)calculate v_n (1) and Σ_n v_n (1) .
let f(x) = ∫_0 ^1 (dt/(2+ch(xt)))
1) find a explicit form of f(x)
2) calculate g(x)=∫_0 ^1 ((tsh(xt))/((2+ch(xt))^2 ))dt
3) find the value of ∫_0 ^1 (dt/(2+ch(3t))) and ∫_0 ^1 ((tsh(3t))/((2+ch(3t))^2 ))dt
4) calculate u_n =∫_0 ^1 (dt/(2+ch(nt))) with n natural integr and study the convergence
of the serie Σ (u_n /n) .