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Hello.
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So here we have that the girl is holding the string four feet above the ground.
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So here, the girl's position is right here.
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So we have four feet here.
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And then we have that the kite is 84 feet above the ground.
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So we have this distance here is 84.
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Now we have that y is equal to 80.
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And if the string is being let out at a rate of two feet per second.
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This means that dzdt is equal to two.
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And then by the pythagorean theorem, or we have that z squared is equal to x squared plus y squared.
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So in this case, we have that y is equal to 80.
00:39
So we have z squared is equal to x squared plus 80 squared.
00:48
So the rate at which the kite is moving horizontally when 100 feet of string has been let out...