1. The problem statement, all variables and given/known data A satellite is in an orbit around earth. The distance from the center of the earth is described by r= 4995/(1+.12cos@) R earth= 3960 mi find the rate at which the altitude is changing at the instant where @=120 degrees. d@/dt= 2.7 degrees/min 2. Notes altitude equals r - (R earth) "@" describes the angle the satellite forms with the Perigee of earth (the closest point) 3. The attempt at a solution a = r - (R earth) = 4995/(1+cos@) - 3960 da/dt= [-4995(-sin@)d@/dt]/(1+cos@)^2 by plugging in the values I get: ~ 46,700 mi/min The answer from back of book is 27.7 mi/min I do find it a mystery that the R earth is not used, that may be a key to solving it. Help!