TransWikia.com

Calculate unknowns in a set of triangles

Mathematica Asked by Johan Grankvist on June 16, 2021

I got a problem of which I can’t get mathematica to calculate.

enter image description here

The known inputs are a=17 degree, b=12 degree and side d is 300.

The whole thing is actually 4 right-angled triangles (left side as A, right side as B, the red at bottom as C and the black with the d side as D)

I’ve tried to type all the equations for the angles and sides I need to get the h value but I can’t get a reasonable output.

Remove["Global`*"]
va = 17;
vb = 12;
d = 300;    
Reduce[{(Tan[va]*(Tan[vc]*d)) == (Sin[va]*(Tan[vd]*d)) == (Tan[vb]*(Cos[vc]/d)) == (Sin[vb]*(Cos[vd]/d)), Tan[vc] == (Tan[vc]*d)/d, Cos[vc] == d/(Cos[vc]/d), Tan[vd] == (Tan[vd]*d)/d, Cos[vd] == d/(Cos[vd]/d)}, h] // N

The ouput I get is

Tan[vc] == -0.275163 Tan[vd] && Sec[vd] == 1.79174 Tan[vd] &&
Sec[vc] == 1.51196 Tan[vd] && Cos[vd] == 161256. Tan[vd] &&
Cos[vc] == 136077. Tan[vd]

What is it that I’m missing?
I can’t see how else I should make the equation more elaborate to get allt the sides and angles that is needed to the the value of h.

2 Answers

Updated code. Now the thing is to only get h value as output

va = 17 Degree; vb = 12 Degree; d = 300;
Reduce[{(h == Tan[va]*(Tan[vc]*d)) == (Sin[va]*(Tan[vd]*d)) == (Tan[vb]*
(Cos[vc]/d)) ==(Sin[vb]*(Cos[vd]/d)), Tan[vc] == (Tan[vc]*d)/d, Cos[vc] 
== d/(Cos[vc]/d),Tan[vd] == (Tan[vd]*d)/d, Cos[vd] == d/(Cos[vd]/d)}] 
//N

Answered by Johan Grankvist on June 16, 2021

va = 17 Degree;
vb = 12 Degree;
d = 300;

Taking x as the length from A to the base of the tower.

Reduce[{
   Tan[va] == h/x,
   Tan[vb] == h/Sqrt[d^2 - x^2]}] // N

x == 171.251 && h == 52.3567

You just need enough expressions to determine your system. If you add too many expressions Mathematica may not find the solution.

Answered by Chris Degnen on June 16, 2021

Add your own answers!

Ask a Question

Get help from others!

© 2024 TransWikia.com. All rights reserved. Sites we Love: PCI Database, UKBizDB, Menu Kuliner, Sharing RPP