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Lighthouse on the Coast
updated 6 months, 4 weeks ago
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A lighthouse is x miles away from the coast. Its beam makes 1 revolution per minute. How fast is the beam moving along the beach, when the point on the beach it lightens up is y miles away from the point on the beach closest to the lighthouse?
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The distance from the base of the lighthouse to the light beam is not going to change as it revolves and it is sqrt(x^2+y^2). So The speed is 2*pi*sqrt(x^2+y^2) per minute.
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