A spotlight on the ground is 100 feet from a building that has vertical sides.(length is apparently infinity) A person 6 feet tall starts at the spotlight and walks directly toward the building at a rate of 5 feet per second.
How fast is the top of the person's shadow moving down the side of the building when the person is 50 feet away from the building?
Step by step instructions would be GREAT. Thanks in advance!
2007-10-30 12:42:55 · 1 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
See my diagram:
http://i13.tinypic.com/5zomxd5.gif
The base of the large triangle is 100.
The small right triangle is similar to the large right triangle. So
x/6 = 100/s
Differentiate both sides with respect to t. We know the value of dx/dt, and we're asked for ds/dt when x=50. (It might be easiest to solve the above for s prior to differentiating; otherwise, you will need to determine the value for s when x=50.)
2007-10-30 13:08:41 · answer #1 · answered by Ron W 7 · 0⤊ 1⤋