See
1/(x-sinx) 0∫x t2dt/√a+t
a+t =b2
2bdb/dt=1
dt= 2bdb
1/(x-sinx)∫(b2-a)2*2bdb/b
[1/(x-sinx)]2∫(b2-a)2db
[1/(x-sinx)]2[b5/5 + a2b -2ab3/3]
b is integrated from a+x to a
\lim_{x\rightarrow 0}\int_{0}^{x}{\frac{t^2dt}{(x-sinx)\sqrt{a+t}}}=1
See
1/(x-sinx) 0∫x t2dt/√a+t
a+t =b2
2bdb/dt=1
dt= 2bdb
1/(x-sinx)∫(b2-a)2*2bdb/b
[1/(x-sinx)]2∫(b2-a)2db
[1/(x-sinx)]2[b5/5 + a2b -2ab3/3]
b is integrated from a+x to a