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Derivatives : Speed of shadow

A tightrope is stretched 30 ft above the ground between Building 1(at point A) and Building 2( point B), which are 50 ft apart. A tightrope walker, walking at a constant rate of 2 feet per second from point A to point B, is illuminated by a spotlight 70 feet above point A.

a) how far from point A is the tightrope walker when the shadow of her feet reaches the base of building 2?(indicate units of measure) PLEASE SHOW WORK

b) how fast is the shadow of the tightrope walker's feet moving up the wall of building 2 when she is 10 feet from point B? PLEASE SHOW WORK

Bldg #1 Bldg #2
--------- ---------
l l l l
l l l l
l l l l
l30 Ft. A------------B l
l high ^l l l
l ^l l l
-------^-->---50 ft---<-------
(between buildings)

Solution Summary

The speed of a shadow is found. The solution is detailed and well presented. A diagram is included.