Answer
(a) $A(r)=4r^2$
(b) $p(r)=8r$
Work Step by Step
(a)
We know that the area of a square is:
$A=side^2$
Each side is equal to the diameter of the circle:
$side=diameter=2*r$
Thus:
$A(r)=(2r)(2r)=4r^{2}$
(b)
We know that the perimeter of the square is:
$P=4*side$
Each side is equal to the diameter of the circle:
$side=diameter=2*r$
Thus:
$p(r)=4(2r)=8r$
