Given,
I(x)=∫esin2x(cosxsin2x−sinx)dx
⇒I(x)=∫esin2x(cosx−2cosx1)sin2xdx
Now let, sin2x=t⇒sin2xdx=dt
I(x)=∫et(1−t−21−t1)dt
Now comparing with,
I(x)=∫et(f(t)+f′(t))dt=etf(t)+c
Here, f(t)=\sqrt{1-t}&{f}^{'}(t)=-\frac{1}{2\sqrt{1-t}}
⇒I(x)=et1−t+c=esin2x⋅cosx+c
Now using, I(0)=1⇒c=0
Hence, the value of I(3π)=21e43