h 上游充廷大￥ The Envelope Theorem 6 SHANGHAI IIAO TONG UNIVERSITY ©Leading out: oc(xo,ao)_dr da Da da a=ao ©The end of the prove.. 2016/12/22Leading out: The end of the prove. 2016/12/22 16 0 0   0 0 0 0 1 (,) , l i i i df d h a c a da a a da aa aa              x x The Envelope Theorem 6