Global Const $fBegin = 1, _
			 $fEnd = 3, _
			 $fStep = 0.0001, _
		 	 $sFunction = "x"

Global $fX, $fX_, $fArea

For $fValue = $fBegin To $fEnd - $fStep Step $fStep
	$fX = Execute(StringReplace($sFunction, "x", $fValue))
	$fX_ = Execute(StringReplace($sFunction, "x", $fValue + $fStep))

	If ($fX_ < $fX and $fX_ > 0) or ($fX_ > $fX and $fX_ < 0) Then
		$fArea += $fStep * $fX_ + ($fX - $fX_) * $fStep / 2
	Else
		$fArea += $fStep * $fX + ($fX_ - $fX) * $fStep / 2
	EndIf
Next

MsgBox(64, "Integral", "Die Fläche des Integrals der Funktion f(x) = " & $sFunction & " an der Stelle: " & $fBegin & " bis " & $fEnd & " beträgt: " & $fArea)