# Reverse the order of integration?

1. Mar 20, 2012

### turbokaz

1. The problem statement, all variables and given/known data

Reverse the order of integration?
Original has it in the form of dy dx, 0<=x<=ln6, 1<=y<=e^x.
I made it dx dy, with 1<=x<=e^y, 0<=y<=ln6
Is this right?

2. Relevant equations

3. The attempt at a solution

2. Mar 20, 2012

### HallsofIvy

Staff Emeritus
Wow, you waited 12 whole minutes before bumping? That's a good way to get banned from this forum!

Draw a graph. x ranges between 0 and ln(6) so draw two vertical lines there. For each x[/itex], y ranges from 1 to $y= e^x$ do draw the horizontal line y= 1 and the $y= e^x$. Notice that $e^0= 1$ so that forms something that looks like a kind of "right triangle" with a curved hypotenuse.

Now, what are the lowest and highest value of y in that "triangle"? Saying that x< ln 6 does NOT mean y< ln 6. y is not x!
Imagine a horizontal line at some y-value. x ranges from the left end of that line to the right end. What are those values?

$y= e^x$ does NOT give $x= e^y$!! Solve $y= e^x$ for x.