The Piper Cherokee has a wing area of 170 ft2 and a wing span of 32 ft.
Its maximum gross weight is 2450 lbs. The wing uses a NACA 65-415 airfoil, which has a lift slope of 0.10331deg^-1 and alpha(L=0)= -3.0deg. Assume that tau = 0.12 . If the airplane is cruising at 120 mph at standard sea level at its maximum gross weight and is in straight and level flight, calculate the geometric angle of attack.