Main Concept

A circle's area can be visualized by a stack of smaller rectangles. Consider a circle inscribed with small inner rings, where each inner ring can be approximated by a rectangle. When stacked on one another, the rectangles assume the shape of a triangle.

We use the formula Area = $\frac{1}{2}$ Base × Height, where we approximate the base as equal to the circle's circumference and the the height as equal to the circle's radius. Using Circumference = 2 × $\mathrm{\π}$ × Radius, the equation for the circle's area takes the form Area = $\frac{1}{2}$ × 2 $\mathrm{\π}$ r × r = $\mathrm{\π}$ $r^2$.

  Radius                               :

Number of Inner Circles    :  

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