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Char. Limit
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Homework Statement
Now this is a problem that my sister had on her Calculus homework, and I can't seem to figure it out. I believe a similar triangles argument is necessary, but I'm not sure, and trig always was my weak spot. The problem is as follows:
A person 2 meters tall walks directly away from a streetlight that is 8 meters above the ground. If the person is walking at a constant rate and the person's shadow is lengthening at the rate of 4/9 m/s, at what rate, in m/s, is the person walking?
Homework Equations
The Attempt at a Solution
Well, we drew a nice triangle like so:
We know that dx/dt = 4/9 and that dX/dt (the x-axis on the larger triangle) is constant. But I can't seem to complete the problem...