[tex]\text{The circumference of a circle}\\\\C=d\pi\\\\C-circumference\\d-diameter\\\\C=d\pi\to\pi=\dfrac{C}{d}\\------------------------------\\\\\text{The area of a circle}\\\\A=\pi r^2\\\\A-area\\r-radius\\\\A=\pi r^2\to\pi=\dfrac{A}{r^2}[/tex]
[tex]EXAMPLE:\\\\d=7\ in\to2d=7\ in\to d=3.5\ in\\C=21.98\ in\\A=38.465\ in^2\\\\\pi=\dfrac{C}{d}\to\pi=\dfrac{21.98}{7}=3.14\\\\\pi=\dfrac{A}{r^2}\to\pi=\dfrac{38.465}{3.5^2}=\dfrac{38.465}{12.25}=3.14[/tex]
