訂正. In article <040527000005.M01473721@ims.kit.ac.jp> Tsukamoto Chiaki <chiaki@kit.ac.jp> writes: > d(df) = d(f' dx) = df'（×）dx + d(dx) = f'' dx（×）dx ! d(df) = d(f' dx) = df'（×）dx + f' d(dx) = f'' dx（×）dx -- 千