趙文川 – Resources – GeoGebra

Euclid's Element, Book I, Proposition 1
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趙文川
MA - 3.1.1 - Def. 2
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趙文川
Copy of Planetary Orbit by Kepler
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趙文川
Copy of Kepler's First Two Laws
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趙文川
径向力守恒定律（几何作图）
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趙文川