Hello, ginax7!

A tightrope is stretched 30 feet above the ground between two buildings which are 50 feet apart.

A tightrope walker, walking at a constant rate or 2 ft/ sec from point A to point B,

is illuminated by a spotlight 70 feet above point A.

How fast is the shadow of the tightrope walker's feet moving along the ground

when she is midway between the buildings?

I am so confused. Where do I start? . . . . Make a sketch! Code:

L *
| *
| *
70 | *
| *
| * T
A * - - - - - o - - - - - - * B
| x * |
30 | * | 30
| * |
* - - - - - - - - - o - - *
C - - - - s - - - - E D
: - - - - - -50 - - - - - :

The tightrope walker is at , having walked feet from to

The spotlight is at , casting the shadow at on the ground.

Let

From similar right triangles, we have: .

Differentiate with respect to time: .

Since ft/sec: . ft/sec.