brian bovril

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15 years, 52 days

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These are questions asked by brian bovril

Hi..

OK, so my real-life example is I have a 3m gap between the house and the garage which I want to hang a sunshade. 
The hanging point on the house is 2.6m high and on the garage 2.1m (above ground). 

I have a choice between 2 sun sails, and I want to know -approximately- what sag I can expect from each.

I realise this is not exactly the same as the hanging wire problem i posted before.. but it my attempt anyway. Can anyone improve?

Sails.mw

there is this ref

https://www.mapleprimes.com/questions/147809-Real-Solution-For-Catenary-Differential-Equation

 

Hi. following on from

https://www.mapleprimes.com/questions/232817-Solving-Hanging-Cable-#comment281577

Second case: unequal poles.

I tried to work with vv's solution, but I got a problem... the required formula is

y=10.85378553130*cosh(0.0921337534371039*x) - 10.85378553130

Uneven.mw

Hi

I am trying to follow this paper

http://euclid.trentu.ca/aejm/V4N1/Chatterjee.V4N1.pdf

Lets start with the easier problem, equal poles. Assume that the length of the cable is 120m and the two poles have equal height of 50m. Our goal is to determine the minimum distance between the two poles that will prevent the cable from touching the ground.

I was trying to get Maple to agree with their derived formula, namely

y(x)= 11*cosh(1/11*x) - 61,

but I think I have not set the IC's correctly. or provided for the length of the cable.

restart:
int(sqrt(1+diff(y(t),t)^2),t=0..x)=120/2

//can't solve the above directly, or maybe someone clever here can

//a is a constant
DIV := diff(y(x), x, x) = a*sqrt(1 + diff(y(x), x)^2);
RV := y(0) = 0, D(y)(0) = -50;
dsolve({DIV});
Opl := dsolve({DIV, RV}, y(x));
allvalues(%)
 

 

Hi

I have a list of records :

S := [`206` = Record(mu = 508.001018040, sigma = 125.002863204708), `4` = Record(mu = 1008.001018040, sigma = 167.707232430134), `2` = Record(mu = 1208.001018040, sigma = 141.512246146314), `5` = Record(mu = 808.001018040, sigma = 117.156800098735)]

How can I extract from S the mu and sd corresponding to a number.

eg input 2 get 1208.001018040,141.512246146314

like this:  rhs(S[3]):-mu, rhs(S[3]):-sigma, (I know from inpection 2 occurs in the 3rd slot but assume i don't know where it occurs). I tried using Search...
 

Hi... I have a long-expression, which I have abbreviated here. I want every 5th term summed. Included is my code, but I need the unassign command (after point 12) for it to work. The problem is when I unhash and insert this unassign('s','X[4]') command into my actual Table of Records procedure, Maple protests. it gives a cryptic: " Error, `(` unexpected " .
How can I modify the original code to sum every 5th term as efficiently as possible as the thing is a 4000 term expression which I later need to numerically integrate?

sum_every_5th.mw


 

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