y=lnsin(3x+2)
y'=[1/sin(3x+2)]*[sin(3x+2)]'
=[1/sin(3x+2)]*cos(3x+2)*3
=3ctg(3x+2).
y=xln3x
y'=ln3x+x*(3/3x)
=ln3x+1.已知y=sin(2x+3),求dy/dx，帮帮忙=2cos(2x+3)