Can you show us how you got that line?
From this:
I'm getting (taking r as a constant):
find the dimensions of the rectangle of largest area that can be inscribed in a circle of radius r
circle:x^2+y^2=r^2
area of the rectangle = 2x2y
y = root(r^2-x^2)
area=(4x)[root(r^2-x^2)]
Area'=4r^2+4xr-8x^2/root(r^2-x^2)
4r^2+4xr-8x^2=(r+2x)(r-x)=0
x=r or x=-r/2
plugging x back into area formula
area = 4(-r/2)[root(r^2-r^2/4)]
area = -r(root3r^2)
the answer is that the sides are [root(2)]r, and that it is actually a square.
Not sure what I'm doing wrong..
also, what happened to the Latex tutorial...?