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๐ŸŒ Archimedes map

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๐ŸŽฏ A demonstration Helionโ€™s concise and powerful graphic capabilities
๐Ÿง  Inspired by Archimedes map by Steve Trettel
๐Ÿ‘‰ Why Is a Sphereโ€™s Surface Area 4ฯ€rยฒ? Visual Proof, No Calculus


From Why Is a Sphereโ€™s Surface Area 4ฯ€rยฒ? Visual Proof, No Calculus:

Why is the surface area of a sphere exactly 4ฯ€r24\pi r^2? Archimedes found the answer over 2,000 years ago, with no calculus.

In this 2-minute visual proof, youโ€™ll see: ๐ŸŠ Why the skin of a sphere covers exactly 4 circles of the same radius
๐Ÿ“ How Archimedes compared a sphere to a cylinder (a can) wrapped around it
๐Ÿ” Why a patch of the sphere and its โ€œshadowโ€ on the canโ€™s wall have the same area: where one stretches, the other shrinks
๐Ÿงฎ Why the canโ€™s wall is 2ฯ€rร—2r=4ฯ€r22\pi r \times 2r = 4\pi r^2

Key idea: sphereโ€™s skin = canโ€™s wall, so they have the same area.

0:00 The orange and the paper circles 0:20 Archimedes and the can 0:40 Patch and shadow: stretched sideways, squeezed toward the pole 1:20 The canโ€™s wall = 4ฯ€rยฒ 1:50 Why this equals 4 circles