ANSWERS: 2
  • The surface of a sphere A = 4(pi)r² equals the circumference times the diameter, that is, 2(pi)r times 2r. This equals the area of a cylinder (ignoring its ends) surrounding the sphere and as tall as the sphere. And THAT's no coincidence, explained at this site that I found on Google: http://mathcentral.uregina.ca/QQ/database/QQ.09.99/wilkie1.html All of this stuff was known by the ancient Greeks.
  • if you draw a circle, and draw a quarter of a sphere over half the circle, resting on the semicircle....now draw a line from the centre of the circle to the top of the quarter sphere, so you have "sliced semicircle" as the edge of the qurter sphere... now imagine the sliced semicirle falling down like a drawbrige onto the circle.... the surface of the quarter sphere will flatten exactly onto the circle

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