| 摘 要： | We establish the concept of shapes of functions by using partial differential inequalites.Our definition about shapes includes some usual shapes such as convex,subharmonic,etc.,andgives many new shapes of functions.The main results show that the shape preserving approxi-mation has close relation to the shape preserving extension.One of our main results shows thatif f∈C(Ω)has some shape defined by our definition,then f can be uniformly approximatedby polynomials P_n ∈p_n(n∈N)which have the same shape in Ω,and the degree of the ap-proximation is Cω(f,n~(-β))with constants C,β>0.
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