optimization question on fences and buildings

sneaky · P versus NP Offline Joined: 17 Oct 2009 Posts: 43

A fence 8 ft tall runs parallel to a tall building at a distance of 4 ft from the building. What is the length of the shortest ladder that will reach from the ground over the fence to the wall of the building? (Give your answer correct to two decimal places.)

can u chow the full steps in doing this?

**Posted:** Fri Oct 30, 2009 10:52 am

Kent Merryfield

Not such a routine problem. The same as the "pipe around the corner" problem. There are some topics that a search of this site using words like that will turn up.

**Posted:** Fri Oct 30, 2009 11:14 am

sneaky · P versus NP Offline Joined: 17 Oct 2009 Posts: 43

there are 2 sites
http://answers.yahoo.com/question/index?qid=20081216082305AAx5lT9
and
http://answers.yahoo.com/question/index?qid=20071114185302AAnuW0Y

but i have no idea whats going on, i cant understand how their describing the diagram, and how they get those calculations, which is why i posted here

**Posted:** Fri Oct 30, 2009 12:46 pm

fedja

Here is the diagram. The red line is the building wall, the green line is the fence, the black line is the ground, and the orange line is the ladder.
$D((0,20)--(0,0),red+linewidth(1)); D((0,0)--(15,0),black+linewidth(1)); MC(90,"8\mbox{\,ft}",8,D((4,0)--(4,8),green...$
Now, can you compute the ladder length $|BL|=|BH|+|HL|$ in terms of the angle $\alpha$ ?

**Posted:** Sun Nov 01, 2009 9:58 am