Classic Cow Grazing Problem

Here's a virtual rendition of the classic [i]Cow Modeling Problem[/i] found in some geometry texts: [br][br][i]A cow is tied by a rope to the corner of a rectangular barn with dimensions __ by ___. [br]Determine the maximum possible grazing area the cow has. [br][br][/i]Yet here, you can change the dimensions of the barn by dragging the corners of the rectangle.
Slide the long slider (at the bottom) slowly to explore where the cow can graze.
For the original dimensions of the barn you were given, what is the maximum possible grazing area the cow has? Show your work and thoughts below and/or in the app above.
– Tim Brzezinski

Information: Classic Cow Grazing Problem