Solución
3
(
1
+
tan
−
1
x
)
2
1
+
x
2
{{3{{\left( {1 + {{\tan }^{ - 1}}x} \right)}^2}} \over {1 + {x^2}}}
1
+
x
2
3
(
1
+
tan
−
1
x
)
2