## Second order PDE February 9 1

Kindly help me with this... $$U_{xy} + yU_{yy} + \sin(x+y)=0$$Here $A =0$, so how to calculate the characteristic equations ?as $$ {dy\over dx} = {B^2 \pm \sqrt D\over2A} $$Let $V=U_y$ ,Then $V_x+yV_y=-\sin(x+y)$Follow the method in http://en.wikiped