Attached is my working of the current problem, but i get an invalid solution. Any help would be appreciated

Thanks

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- Apr 5th 2013, 07:24 AMMMCSCalculus - Maximum length of ladder
Attached is my working of the current problem, but i get an invalid solution. Any help would be appreciated

Thanks - Apr 5th 2013, 08:02 AMhollywoodRe: Calculus - Maximum length of ladder
I'm not sure what happened on the last step: You have , which should give you:

, so x is approximately 0.7375 radians or 42.3 degrees.

That gives you a ladder length of .

- Hollywood - Apr 5th 2013, 08:39 AMMMCSRe: Calculus - Maximum length of ladder
thanks for your reply hollywood, Is it possible for you to exaplain how you got from what i had to what you have as i am new to calculus

Thanks - Apr 5th 2013, 06:04 PMhollywoodRe: Calculus - Maximum length of ladder
Sure, but you already did the hard part...

Starting with your equation (recall you took the derivative and set it equal to zero):

add to both sides:

multiplly both sides by and combine the trig functions:

Then take the cube root and inverse tangent to get x=0.7375. But you want the length of the ladder, so you have to plug in to the original equation:

.

- Hollywood - Apr 7th 2013, 12:37 AMnimonRe: Calculus - Maximum length of ladder
Interesting, I was just doing this problem in a book I'm reading. The solution I found doesn't use the angle at all, but instead labels the lengths with new variable names and finds a relationship between them in terms of the known variables. The answer is given in terms of and and I thought you might find it interesting. It's attached to my reply.