# circumference

## π Enters the 5th Class

I write this to tell myself that it was not a dream...

This year I taught a bunch of fifth standard kids in Sahyadri School KFI (Krishnamurti Foundation India), who, like all others of their age, were high-energy kids; they were willing to explore but found it difficult to sit down in one place. I had a great relationship with them. The air in the classroom was of love, trust and wonder!

## An Approximation of pi by the Law of Cosines

The approximation of π is a popular pastime of students of mathematics and I have started with the familiar age-old way, of fitting a regular polygon tightly in a circle of radius r. The vertices of the n-sided polygon are joined to the centre of the circle so that the angle subtended at the centre by each segment is 360/n. If n is sufficiently large, the perimeter of the polygon approaches the circumference 2πr of the circle and this approximation improves as the number of segments increases.

## Scale of Earth & Sun

It’s hard to imagine the scale of the solar system and the universe. This video, on the scale of the earth and the sun, helps in getting a sense of scale and speed.

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