Need a math whiz

I’d like to know the angle in question is within the parameters as follows:

80<anglex<110 - where anglex is the calculated value.

I know several things - I know the length of side a and side b, therefore, I can calculate side c using pythagorean theorom .

and so from what i’ve checked if I know all three sides of a triangle, I can use that to calculate all the angles of said triangle.

I found a formula says

anglex = arccos ((aa + bb - cc)/2a*b))

or said in english anglex is equal to the arc cosine of a squared plus b squared minus c squared all divided by 2 times a times b.

EDITED - oops real quick as I need to go, but There is a fundamental issue here - I mistakenly said the pythagorean theorom would help me find the third side – -- although this is true for a right triangle, I don’t actually know I have a right triangle – that is somewhat what I am trying to find out. is the angle between 80 and 110 - or in otherwords sort of a right triangle. but the question below is still valid.

So I test my new found formula with the KNOWN 3,4,5 right triangle.

so 3 squared plus 4 squared is 25 minus 5 squared yep 0

so the angle x is equal to the arccos(0) and i get 1.5708

So what does this mean? I know that in a 3,4,5 right triangle there is NOT an angle that is 1.5708.

So I am missing the next step???


If I understand your question, you don’t know the third side of your triangle, and you don’t know whether you have a right triangle. Am I right?

In order to “solve” your triangle, you must have any combination of three sides and angles.

If you can accurately determine the three sides of your triangle, then the formula opposite the red arrow below can be used to find any (or all) of the angles.

If you know some other combination of three sides and angles, then one of the other formulas shown will give you what you’re looking for.

And so I am back and did some more research - I think the number I came up with 1.5708 is a radian measure.


I found another statement, that 1 radian is 57.3 degrees. So without further ado

1.5708 * 57.3 is approximately 90.00

I do not know that I am accurate, but I believe I am. as 90 is about the number I was expecting.

So I’ll just do a few more quick tests - - see if I can get within the 80 to 110 degree category.

A quick thought here - then
X57.3 = 80 then lower bound x = 1.396160558 radians.
57.3 = 110 the upper bound x = 1.919720768 radians.

if anyone sees wrong trig here let me know. thanks

It looks like yes your right on track of where I am trying to go. . . see my other post ; does it make sense to you?

I think I know the third side, so I know SSS and so I am looking for the angle that most closely represents a 90 degree angle.

might as well admit it -
I only know 2 sides.

so if someone can fill me in on how to find the angle(s) solve the triangle - when you ONLY know SS -

So to the real question- I want to know, when line A turns at about a 90 degree angle into line b

So now I think i’ll research some slope formula’s and see if that’ll help

are you saying the lengths of only two sides are known and the angle of those two sides is not known ?

I think this kind of work has been done and is available on the net, look for MT4 indicators relating to Harmnoics and Gartley patterns.

Correct -
I KNOW Side Side and that is it - nothing else.

So it is impossible to solve the rest.

I am working around the issue, so we’ll see if it works.

THanks everyone for your input and suggestions.

To convert radians to degrees:

X *180/3.1416