Circle Area with a Parallelogram

I made this way back in middle school in Adobe Flash CS4. (This was before Adobe changed the name.) It is a Windows executable that animates sectors of a circle being rearranged into a pseudo-parallelogram. This helps you visualize why the formula for the area of a circle works.

I also had a website in middle school. It was a different website than this one. The text below was taken from an archive of my old website.

Text from My Old Website

The Circle Area Visualizer dynamically visualizes the area formula of a circle. The user drags the center and a point to form a circle, which is automatically sliced into the given number of sectors. By dragging the sliders at the bottom or using the animation buttons, the user can rearrange the sectors into a pseudo-parallelogram, from which the area formula of a circle is derived. Below is the algebra behind the area formula of a circle, based on the parallelogram attained with the method that Circle Area Visualizer illustrates.

The algebra behind the area formula of a circle

The current version of the Circle Area Visualizer is 1.2. Download the Windows executable!

Note: The screenshots below were taken with Version 1.1 of the program.

Circle Area Visualization 1.1 - Circle Circle Area Visualization 1.1 - Mid-Process Circle Area Visualization 1.1 - Pseudo-Parallelogram