By continuity <By the continuity> of f,......
By assumption,......
By the above,......
By the induction hypothesis,......
By and large, we shall use the same notation as in...... [= In general]
term-by-term differentiation
a 3 by 4 matrix = a 3× 4 matrix
Thus we need only alter our constants by a factor of 2 to deal with this case.