So there are three ways to do this. If you have 2 sides of the triangle you can use SOH-CAH-TOA to find the other angles. S= sin, O= opposite side of the angle, H= hypotenuse. The hypotenuse is the longest side of the triangle. C= cos, A= adjacent, adjacent means the side next to the angle, H= hypotenuse. T= tangent, O= opposite, A= adjacent. You could take 180 and subtract 55 to figure out what you have left then you can figure out what you need to do next. The other way that I can think of is to use the law of sines which is sin A/ A, Sin B/B, Sin C/C. You can use this to equal Sin A/A = Sin C/ C or any combination as long as you don't mix them together like Sin A/ C because it just wouldn't work. Sin= the angle and A,B, and C equals the sides so if you say Sin A you are saying angle A. This can work if you have two sides. You would set it up as Sin 55/what ever side is A which is = to let's say Sin C/ whatever side is C. Then you can cross multiply to say whatever side is C sin 55/whatever side is A = Sin C then you use your calculator to Sin-1 the answer to get what the angle of C is. Then add them together and subtract from 180 for the last angle.
The sum of the angles is 180 degrees. How do you find the other two angles if the third angle is 55 degrees??
You can't do it unless you know another angle or the two sides adjoining 55*.
You could do this: 180 - 55 = 125. So the sum of the other 2 angles is 125.
Call one of those A & the other B.
A + B = 180 --> B = 180 - A
The other 2 angles are A and 180 - A.