root [11] TF1 *f1 = new TF1 ( "f1" , "sin(x)/x" , 0 . , 1 0 . ) ;
root [12] f1->Draw ( ) ;

root [ 1 3 ] TF1 *f1 = new TF1 ( "f2" , "[0]* sin ([1]*x)/x" , 0 . , 1 0 . ) ;
root [ 1 4 ] f1->SetParameter ( 0 , 1 ) ;
root [ 1 5 ] f1->SetParameter ( 1 , 1 ) ;
root [ 1 6 ] f1->Draw ( ) ;