Topic: Math question: find height from distance and two angles

[paulmcz]

Your correction would work only if both angles were less than 90 deg.

[MeasureUp]

Your correction would work only if both angles were less than 90 deg.

Not really. It works for angles greater than 90deg as well.

From your code the height = 3192.2655
while the height measured on the drawing = 2149.1800, which is based on these:
Angle a = 90.8933333333 deg
Angle b = 85.434722222 deg
Distance = 205.12

[Kerry]

I think you guys need to go back and define your terms.

The decision to add or subtract the divisor components depends on the way the larger angle is measured.
You are using different criteria.

[Kerry]

For instance :
using the internal angles as per the sketch attached is correct.

Using (- pi (dtr 100)) as Paul has done requires the divisor components be negated (as he has done).

So you are both correct, or both incorrect or whatever

[Kerry]

In answer to a PM.
The app is 'Pencil' ..
http://pencil.evolus.vn/Features.html

[MeasureUp]

Thanks to Kerry's explanations.

OK, lets go back to the starting point.
I don't know if Alan has already looked Paul's drawing.
I know that is not easy when translating the words to the drawing.
Generally speaking, our discussions should be all based on the same coordinate system, which means that all angles measured anticlockwise from X axis.
By looking at your drawing, the angle "A" you described actually differs to what Alan given.
Alan's: 90°53'36"
and yours: 180° - 90°53'36" = 89°06'24"
This explains why you got the height of 3192.2655
In other words, the angle "A" in your code can be simplified to:
(setq a (dtr 90.8933333333))

I attache my version here. Hope I have not misunderstood Alan's issue.

[Kerry]

MeasureUp,
Your triangles are acute ;
Pauls is obtuse


I guess this whole thread is a perfect example of one of my favourite topics .. making sure we are all answering the correct question.

added:
For what it's worth, my assumptions about the problem were the same as Pauls ie the angles given represented the internal triangle angles.

[MeasureUp]

MeasureUp,
Your triangles are acute ;
Pauls is obtuse


I guess this whole thread is a perfect example of one of my favourite topics .. making sure we are all answering the correct question.

Thanks Kerry, again.
We shall now wait and see what Alan will say. 
Of course, Paul can check if I haven't miss any points from you.

[paulmcz]

As Kerry is saying, your triangle is acute. But, Alan specified one angle acute and the other obtuse.

[CAB]

Strange, I would always assumed we were talking Internal Angles with a triangle.
Other wise the orientation of the triangle comes into play. 

[Rob...]

Strange, I would always assumed we were talking Internal Angles with a triangle.

<fake southern drawl>That's the way I was learnt to do it.

[MeasureUp]

By looking at Paul's drawing again, lets think in this way, we now draw 2 construction lines.
One to the angle of 90.8933333333deg and another to 85.434722222deg.
If the 1st one placed on left while the 2nd on the right, we all know that they never intersect physically.
This is what the info was given by Alan.
It only makes sense if the 1st construction line drawn on the right.
Agree?
If we have a building/civil/survey background, we may better understand the info which Alan's given.
Hope I have explained what I think clearly.