Concept:Use the substitution x=tant to simplify the inverse trigonometric expression, then integrate by parts.Explanation:Let x=tant, so dx=sec2tdt.Then 1+x22x=1+tan2t2tant=sec2t2tant=2sintcost=sin2t.So the integral becomes I=∫sin−1(sin2t)sec2tdt=∫2tsec2tdt.Integrating by parts: I=2[ttant−∫tantdt]=2ttant+2ln∣cost∣+c.Since t=tan−1x, we have tant=x and cost=1+x21.Thus I=2xtan−1x+2ln1+x21+c=2xtan−1x−ln(1+x2)+c.Answer:2xtan−1x−ln(1+x2)+c, which corresponds to option A.