My initial approach was to start with
A = bh = x.cos(x)
and then evaluate A'=0 to find the points but I got stuck in the process, I missed something or maybe I'm evaluating the wrong area.
Find, correct to five decimal places, the dimensions of the rectangle of largest area that has its base on the x-axis and its other two vertices above the x-axis and lying on the curve .
I have no idea where to begin... I don't even be clear what it wants for the result
But this problem, as stated, has no solution. Taking the left side at , we can take the right side at having arbitrarily large area. There is NO "largest area".