Question

A fireman has to reach a burning building. Determine the length of the shortest ladder that will reach over a 2 metre high fence to the burning building which is 1 metre behind the fence.

Need the 2 Equations to sub so I can then take derivative and set to 0! someone please find my 2 equations I have the length of ladder one but need the limiting equation!!!

Answer 1

z² = x² + y²

Answer 2

yes, and now the limiting equation? that I will use to substitute into c^2 = a^2 + b^2 to obtain a single variable on the right side and then do the derivative

Answer 3

the length of ladder is limited!

Answer 4

=> xdx/dt + ydy/dt = 0

Answer 5

do I need to carry the exponent on Z over before deriving?

Answer 6

It's constant, so "No"

Answer 7

ok so I have \[L^2 = (y+1)^2 + (x+2)^2\]

Answer 8

Do you post the whole problem at all?

Answer 9

yea thats the whole thing

Answer 10

see what I mean I need a second equation to limit that one to one variable before I can derive

Answer 11

Is it Related Rate problem? because without the data of dx/dt and dy/dt, it doesn't look right!

Answer 12

no its a optimization problem from grade 12 calculus... part of a take home assignment

Answer 13

Let me check, but keep Z to take derivative first!

Answer 14

Do you how to apply similar triangles?

Answer 15

xy = 2 => y = 2/x That's limitation!

Answer 16

OK i had that before, so I am subbing that into the original hypotenuse equation the deriving and setting to zero?

Answer 17

then*

Answer 18

After taking derivative, subs y = 2/x, solve for x, y, z

Answer 19

so take the derivative of L2=(y+1)2+(x+2)2 then sub?

Answer 20

sorry the 2s are exponents

Answer 21

?

Answer 22

wait I'm not following, I gotta start from the beginning