When the direction of forces is popularly explained, they say "the lifting force is directed perpendicularly, and the drag force is parallel to the oncoming flow".
But what if it's a swept wing? In that case, which variant is more correct and why? Will the chosen variant apply to all objects affected by aerodynamic forces and, if not, what are the exceptions?
Also, if in reality the forces are directed as in the second variant, are most of the further formulas created in such a way as to obtain a mathematical model of the first variant? For example, the lift curveslope of a swept wing will be less than that of a straight wing - is this the result of a conversion between models? I would appreciate as much information as possible, because I want to have a solid idea.