While deriving the standard equation of an ellipse, the identity b2=a2−c2 is introduced. What is the chief purpose of bringing this identity into the algebraic steps?
(a) To maintain dimensional consistency of the algebraic steps
(b) To express the eccentricity e solely in terms of a and b
(c) To replace c so that the equation no longer contains the focal distance
(d) To relate the semi-minor axis b directly to c for later substitution