Drag per unit span 

For small ,  (in radians) 

i.e.

 
 

Drag due to angle of attack, thickness and camber

Consider a cambered airfoil at angle of attack.

The slope  of the airfoil surface is the sum of the slopes due to the angle of attack, the camber and the thickness distribution.

Similarly, 

Now,

Giving,

Note:

1. Everything causes drag.
2. We can split up the airfoil at the angle of attack into

(a): flat plate at AOA
(b): camber line at zero AOA
(c): thickness distribution at zero AOA
 

Pitching Moment

Pitching moment due to the net force at a distance x from the leading edge on an area (dx times 1) is

Moment coefficient is

If we split q as before into AOA, camber and thickness, we will find that

1. the contribution of thickness is zero
2. both AOA and camber cause pitching moment

Aerodynamic Center

It is the point about which the pitching moment is independent of angle of attack. The above equation shows that the aerodynamic center is at the mid chord.