Anita A. answered • 12/02/15

Tutor

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Instructor of Finite Mathematics at the Community College Level

Labeling the horizontal axis [0,40] and given that the rate of change (or dx) is 5 fps, y = 6 and recall that x

^{2}+ y^{2}= c^{2}.Take the derivative implicitly to get 2x dx + 2y dy = 0. At a distance of 10 feet from the wall, x = 30, y = 6, you get

2(30)(5) +2(6)(dy) = 0

300 + 12 dy = 0

12 dy = -300

dy = -12 fps

The length of the shadow on the building When the man is 10 feet from the building is decreasing at a rate of 12 fps.