MsgBox(64, "Integral", "Die Fläche des Integrals der Funktion f(x) = " & "x^2" & " an der Stelle: " & "1" & " bis " & "3" & " beträgt: " & _Integral("x^2", 1, 3))

Func _Integral($sFunction, $fBegin, $fEnd, $fStep = 0.0001)
	Local $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

	Return $fArea
EndFunc