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.

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.