Hi, I'm a bit confused by induced drag on an aerofoil and hoping somebody can clear it up for me. I understand that as air slips around the edges of the wing due to the pressure differential between the top and the bottom surfaces, the angle of attack at the ends of the wings is effectively reduced(as the air is being deflected downward). What i'm unclear about is, some sources seem to state that component of lift opposing motion is the induced drag(i.e. if the wing is at an angle with respect to the airflow, the wing generates a force perpendicular to it, and a component of that is lift and a component of that is drag) Below is an image illustrating the latter: http://selair.selkirk.bc.ca/training/aerodynamics/images/induced-definition.gif [Broken] So my question is, is induced drag due to downwash from wingtip vortices, or the rearward component of lift since the force the wings generate isn't directly upward. Or is it a combination of both of these things?