Question 1193964
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The z=6t measures the boy's distance from the foot of the ladder at time t.  Since the ladder is inclined at 60 degrees to the horizontal, his vertical distance from the ground is y=(3*sqrt(3))t and his horizontal distance from the base of the wall is x=A-3t, where A is the distance from the base of the wall to the foot of the ladder.<br>
Both those functions are linear, so the rates of change of his vertical distance from the ground and of his horizontal distance from the foot of the wall are constants.<br>
ANSWERS:<br>
(1) rate at which his vertical distance from the ground is changing = dy/dt = 3*sqrt(3)<br>
(2) rate at which his horizontal distance from the foot of the wall is changing = dx/dt = -3<br>