> f[1]:=8*sin(Pi*xi)/Pi^3/(1-xi)/xi-1;

                              8 sin(Pi xi)
                     f[1] := --------------- - 1
                               3
                             Pi  (1 - xi) xi

> f[2]:=sin(Pi*xi)/Pi/(1-xi)/xi-1;                                      
>                                                                       
>                                                                       
>                                                                       
>                            

                                sin(Pi xi)
                      f[2] := -------------- - 1
                              Pi (1 - xi) xi

> f[3]:=2*sin(Pi*xi)/Pi^2/(1-xi)/xi-1;        

                              2 sin(Pi xi)
                     f[3] := --------------- - 1
                               2
                             Pi  (1 - xi) xi

> f[4]:=1/4*sin(Pi*xi)/(1-xi)/xi-1;  

                                 sin(Pi xi)
                     f[4] := 1/4 ----------- - 1
                                 (1 - xi) xi

> plot({f[1],f[2],f[3],f[4]},xi=0..0.5, numpoints=8,style=line); 

> 
