Application of calculus
A lamp is placed on the ground 100ft away from a wall. a max 6ft tall is walking at a speed of 10ft/sec from the lamp to the nearest point on the wall. When he is midway between the lamp and the wall , the rate of change in the length of his shadow is (in ft/sec)?
On my website you'll find similar problems with animations
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On the optimization and related rates page see walking towards the light and walking away from the light