Write out the equations for area of a circle and perimeter (circumference) of a circle:
A=pi*r^2 =pi*r*r
p
C=2pi*r = perimeter = p = 2*pi*r so p = 2*pi*r, or r=------
2*pi
substitute this last result into the formula for A:
p
A = pi [---------- ]^2 This formula has only one independent variable, 2*pi p. So, upon simplification of this formula, you'll
end up with a formula for A in terms of p.