Don't include the answer, just tell me the process!

It would probably help you if you drew the situation.  First realize that the length of the rope is larger than one of the dimensions.  If you allow the rope to line up with the side of larger dimension it can only sweep out an arc until it touches the opposite side.

The angle swept out can be found by realizing that sina=smaller dimension / length of rope  in this case:

sina=smaller dimension/ rope length

a=arcsin(smaller dimension/ rope length)

So the sector area is:

A=p(rope length)^2(a/360)

What remains other than the sector area a triangle with a width of the smaller dimension and a height of h=√(rope^2-width^2)

The area of this triangle is just: A=(w/2)*(√(rope^2-width^2))

Then you just add the sector area to the triangle area and you will have the area the tiger can access.