text: where 
  
  Dil= induced drag corresponding to some orig- 
  
  inal altitude density ratio, 0, 
  
  D&= induced drag corresponding to some new 
  altitude density ratio, q 
  
  (and L, S, AR, V are constant) 
  
  This relationship 
  induced drag 
  increase with altitude, e.g., a given 
  would 
  airplane flying in level flight at a given TAS 
  at 40,000 ft. (u=O.25) would have four times 
  as much induced drag than when at sea level 
  (u= 1.00). This effect results when the lower 
  
  implies that 