TeX source:
\begin{array}{ccllrcl}\quad\mathbb{D} &=& \mathbb{R}\\\\f(x) &=& 2x\cdot 3\sin(x)\\&=& 6x\cdot\sin(x)\\\\\quad u(x) &=& 6x &\Rightarrow & u'(x) &=& 6\\\quad v(x) &=& \sin(x) &\Rightarrow & v'(x) &=& \cos(x)\\\\f'(x) &=& 6\cdot\sin(x)+6x\cdot\cos(x)\\&=& 6\left(sin(x)+x\cos(x)\right)\\\end{array}