[问答题]
Farmer Thomas wants to build a
n( xobht now)(k++ ;xb e7g yk iujm*+;sheep farming field in the shape of a rectangle with semicircles of radius r on two sides, as shown on the diagram. He has decided to use in total 350 metre
ig;*m 7euy+k js of wooden fencing.
1. 1. Find an expression for the area of the farming field in terms of r .
2. Find the width of the farming field when the area is a maximum.
2. Show that in this case the length of the rectangle is equal to zero and the farming field is the circle of radius 175 $\pi^{-1}$ metres.
