The value of I=2∫sinxsin(x−π/4)dx is
x+log|cos(x−π/4)|+C
x−log|sin(x−π/4)|+C
x+log|sin(x−π/4)|+C
x−log|cos(x−π/4)|+C
Put x−π/4=t
I=2∫sin(π/4+t)sintdt=∫(cott+1)dt=t+log|sint|+C′=x+log|sin(x−π/4)|+C,C=C′+π/4