∫sinxsin(x−a)dx=
xsina+cosalogsinx−a+C
cosx+sinxlogsinx−a+C
(x−a)cosa+sinalogsin(x−a)+C
xcosa+sinalogsin(x−a)+C
I=∫sinxsin(x−a)dx
=∫sin(x−a+a)sin(x−a)dx=∫sin(x−a)cosa+cos(x−a)sinasin(x−a)dx=∫[cosa+sinacot(x−a)]dx=cosa∫dx+sina∫cot(x−a)dx=xcosa+sinalog|sin(x−a)|+C