Basic calculation problem

[Kendon]

Hi all first post on here so here goes. I am doing my Masters and have a calculation that looks fairly easy to resolve as I have all the given figures however I seem to be coming up with a different answer from someone else who is adamant he is right. I have all the values for the formula so either its my lack of knowledge in the use of the calculator or a wrong interpretation of the figures. Here is the equation. Its to do with heat transfer from a smokey layer to the ground effectively. I need to find the value of F^12 to go into another equation.

X =9/2.05 =4.39 Y= 12/2.05 = 5.854
F^12 = (2/(PI *4.39*5.854) Big Brackets Ln sqroot [((1+4.39^2)(1+5.854^2)/(1+4.39^2+5.854^2)] + 4.39 sqroot (1+5.854^2) tan-1 (4.39/sqroot 1+5.854^2)+5.854 sqroot (1+4.39^2) tan-1((5.8540/sqroot 1+4.39^2)) - 4.39 tan-1(4.39) -5.854 tan-1(5.854) end of big brackets.

I hope this makes sense. I get 1.164 however my friend is adamant its 107 which would give the next equation a figure that would look more accurate.
I hope this is ok.
Thanks in advance

 

[Kendon]

Hi mate i am struggling to attach the word or anyother type of file so you can see it.
Yes LN is for {LN SQRT[(uv) / (1 + x^2 + y^2)] } part of the equation
I make tan-1 (5.854) = 1.4016

The rest of the equation looks right how you have written it.
I have just calculated
u = 20.2721
v = 35.269316
F^12 = [2 / (PI xy)] total so far in equation
* {LN SQRT[(uv) / (1 + x^2 + y^2)] = 1.24697
+ x SQRT(v) TAN-1(x / SQRT(v)) = 17.8428
+ y SQRT(u) TAN-1(y / SQRT(u)) = 41.9643
- x TAN-1(x) - y TAN-1(y)} = 27.8467 x (2/pi x 4.39 x 5.854) = 0.689821

Am i doing some drastically wrong. Admitedly I havent carried out maths formulas like this for 10 years but it shouldnt be hard to get to a figure. A colleague got 107

Thanks in advance
Ken

 

[Bob Brown MSEE]

Hi all first post on here so here goes. I am doing my Masters and have a calculation that looks fairly easy to resolve as I have all the given figures however I seem to be coming up with a different answer from someone else who is adamant he is right. I have all the values for the formula so either its my lack of knowledge in the use of the calculator or a wrong interpretation of the figures. Here is the equation. Its to do with heat transfer from a smokey layer to the ground effectively. I need to find the value of F^12 to go into another equation.

X =9/2.05 =4.39 Y= 12/2.05 = 5.854
F^12 = (2/(PI *4.39*5.854) Big Brackets Ln sqroot [((1+4.39^2)(1+5.854^2)/(1+4.39^2+5.854^2)] + 4.39 sqroot (1+5.854^2) tan-1 (4.39/sqroot 1+5.854^2)+5.854 sqroot (1+4.39^2) tan-1((5.8540/sqroot 1+4.39^2)) - 4.39 tan-1(4.39) -5.854 tan-1(5.854) end of big brackets.

I hope this makes sense. I get 1.164 however my friend is adamant its 107 which would give the next equation a figure that would look more accurate.
I hope this is ok.
Thanks in advance

 

[HallsofIvy]

I started trying to do that on a calculator but got lost!

So I wrote a Java program:
Double X= 4.3902439;
Double Y= 5.8536585;

Double U= Math.sqrt(1+ X*X);
Double V= Math.sqrt(1+ Y*Y);

Double A= Math.log(U*V/Math.sqrt(1+ X*X+ Y*Y));
Double B= X*V*Math.atan(X/V)+ Y*U*Math.atan(Y/U);
Double C= X*Math.atan(X)+ Y*Math.atan(Y);

Double Z= A+ B- C;

and got Z= 27.88638.

 

[Kendon]

Agree; got same results with UBasic:
but you forgot to multiply that by [2 / (pi*x*y)], which gives .6908

What makes not much sense is 2 / (pi*x*y) = .02477;
so in order to end up with the "adamant!" result of 107,
we need: .02477(A + B - C) = 107, so A + B - C = ~4320 (far cry from ~28).
And no way can A+B-C equal 4320 with the given data/terms...

So Kendon, to put it gently, you're losing your time ... plus ours!

Denis and all
Many thanks for your help. I am glad it wasnt me. Thank you for showing me the way to break the equation down to make it easier to handle.
Have a good weekend
Ken