 }
 { $examples
     { $example
-        "USING: math.derivatives math.trig prettyprint ;"
+        "USING: kernel math.derivatives math.functions math.trig prettyprint ;"
         "60 deg>rad [ sin ] derivative-func call ."
         "0.5000000000000173"
     }

{ $examples
    { $example
        "USING: math math.derivatives prettyprint ;"
        "[ sq ] 4 derivative ."
        "8"
    }
    { $notes

    }
} ;

HELP: (derivative)
{ $values
    { "x" "a position on the function" }
    { "func" "a differentiable function" }
    {
        "h" "distance between the points of the first secant line used for "
        "approximation of the tangent. This distance will be divided "
