How is induced drag calculated and what design features minimize it?

Induced drag coefficient CDi = CL^2 / (pi * e * AR) where e is Oswald efficiency factor (0.7-0.9 typically) and AR is aspect ratio. Induced drag arises from wingtip vortices creating downwash that tilts the lift vector. Design features to minimize induced drag include: high aspect ratio wings, winglets or raked wingtips, elliptical lift distribution (achieved with tapered or twisted wings), and proper wing-body blending. At cruise, induced drag may be 40-50% of total drag for airliners.