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symbolic integration

I am reading about Symbolic Integration from Manuel Bronstein's
Symbolic Integration 1 and some references therein.

>From the articles:

"Indefinite and Definite Integration" by Kelly Roach (1992)
"The evaluation of Bessel functions via G-function identities" by
Victor Adamchik (1995)
"Definite Integration in Mathematica 3.0" by the same author
"Symbolic Definite Integration" by Daniel Lichtblau

I was able to figure out a lot of things on how Mathematica determines
indefinite and definite integrals.

What I don't understand (and I can't find any clear reference
anywhere) is how
Mathematica having evaluated an antiderivative "searches for" and
"figures out" possible singulaties in the integration range.

For example here (*non-integrable singularity at x=1/2*)

Block[{Message}, Integrate[1/(x - 1/2), {x, 0, 1}]]

and here...

Integrate[1/Sqrt[x], {x, 0, 1}] (*integrable singularity*)

Also how about here

Integrate[1/(2 + Cos[x]), {x, 0, 2*Pi}]

where in this example the integrand is a continuus function of x
but the indefinite integral return by Mathematica has a finite
at x=Pi

Integrate[1/(2 + Cos[x]), x]
Show@Block[{$DisplayFunction=Identity},Plot[%, {x,#[[1]],#[[2]]}]&/



Integrate[Log[Sin[x]^2]*Tan[x], {x, 0, Pi}]
Integrate::idiv : Integral of Log[Sin[x]^2]*Tan[x] does not converge
on \
Integrate[Log[Sin[x]^2]*Tan[x], {x, 0, Pi}]

Of course the integral is convergent.


Integrate[Log[Sin[x]^2]*Tan[x], {x, 0, Pi/2, Pi}]

Plot[Log[Sin[x]^2]*Tan[x], {x, 0, Pi}];
f = (FullSimplify[#1, 0 <= x <= Pi] & )
[Integrate[Log[Sin[x]^2]*Tan[x], x]]
(Plot3D[Evaluate[#1[f /. x -> x + I*y]], {x, 0.01, Pi}, {y, 0.01, Pi},
PlotPoints -> 50] & ) /@ {Re, Im};

Any insight will be greatly appreciate.

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