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

Global $fX, $fX_, $fArea

For $fValue = $fBegin To $fEnd - $fStep Step $fStep
	$fX = $fValue
	$fX_ = $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(0,"",$fArea)