function?[CXY]=chebyshev（funnab）
%Input??-fun?is?the?string?function?to?be?approximated
%???????-n?is?the?degree?of?the?chebyshev?interpolating?polynomial
%???????-a?is?the?left?end?point
%???????-b?is?the?right?end?point
%???????-C?is?the?coefficient?list?for?the?polynomial
%???????-X?contains?the?ab