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But for now, if you slice a cone parallel to the base,
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you'll get a circle;
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at an angle, you'll get the ellipse.
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So, that's the first statement.
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Second statement is the following:
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If you pick one planet and it's there today,
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you wait a week, it's there,
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and you wait another week it's there.
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You join these two lines
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and you call that the area swept out by the planet in the first week;
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then, in the second week, the area swept out is that.
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So, it's the area intercepted by the two radial vectors