c = circumference of circle
p = perimeter of square
c + p = 29
p = 29 - c
side of square = (29 - c)/4
radius of circle = c/(2pi)
a = side^2 + (pi)r^2
a = ((29 - c)/4)^2 + pi * (c/(2pi))^2
a = (1/16)(841 - 58c + c^2) + (c^2/(4pi^2)) * pi
a = 52.5625 - 3.625c + c^2/16 + c^2/(4pi)
Since the 2nd degree term has a positive coefficient is positive, this has a graph that is a parabola opening up. It has a minimum value.
We take the derivative of the area expression and set equal to zero to find the minimum circumference.
da/dc = -3.625 + c/8 + (c/(2pi)) = 0
c = 12.76
Answer: 12.76 cm
