so I tried to program the following matlab/octave code, but it is proved not work
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octave:1> function z=f2(x)
> z = x^2;
> endfunction;
octave:2> function z=f(x)
> z=9*quad(@f2, -sqrt(9-x^2), sqrt(9-x^2))-3*x;
> endfunction;
octave:3> quad(@f, -3, 3)
error: quad: invalid recursive call
error: evaluating binary operator `*' near line 2, column 10
error: evaluating binary operator `-' near line 2, column 47
error: evaluating assignment _expression_ near line 2, column 8
error: called from `f'
error: quad: evaluation of user-supplied function failed
octave:3>
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please help
eric